Usability Heuristics for Metaverse

Abstract

The inclusion of usability heuristics into the metaverse is aimed at solving the unique issues raised by virtual reality (VR), augmented reality (AR), and mixed reality (MR) environments. This research points out the usability challenges of metaverse user interfaces (UIs), such as information overloading, complex navigation, and the need for intuitive control mechanisms in these immersive spaces. By adapting the existing usability models to suit the metaverse context, this study presents a detailed list of heuristics and sub-heuristics that are designed to improve the overall usability of metaverse UIs. These heuristics are essential when it comes to creating user-friendly, inclusive, and captivating virtual environments (VEs) that take care of the needs of three-dimensional interactions, social dynamics demands, and integration with digital–physical worlds. It should be noted that these heuristics have to keep up with new technological advancements, as well as changing expectations from users, hence ensuring a positive user experience (UX) within the metaverse.

1. Introduction

The notable advancements in information and communication technology (ICT) are becoming more apparent every day. In the last 30 years, many technological advances have impacted our interactions with the surrounding environment and our daily lives, such as the internet, mobile phones, and personal computers (PCs). The development and use of virtual worlds are considered to be among the latest developments in ICT, which mainly stemmed from the development of Internet technology.

In virtual world technology, there are four prominent terms: extended reality (XR), VR, AR, and MR. However, it is crucial to understand the differences between these terms and what they mean. XR or Cross Reality is an umbrella term encompassing immersive technologies and electronic, digital environments in which data are displayed and projected [1]. Thus, XR includes VR, AR, and MR [1,2]. VR is an artificial environment that has been built entirely digitally. This environment gives users the impression that they are immersed in a new environment and can interact with it just like their physical surroundings [3]. Thus, VR technologies can transform the entertainment industry, remote work, marketing, economics, and education [1]. With the help of specialized multisensory equipment such as immersion helmets, VR headsets, and omnidirectional treadmills, this experience is amplified through the modalities of vision, sound, touch, movement, and the natural interaction with virtual objects [4,5]. While AR takes a different approach to physical places, it integrates digital inputs and virtual features into the actual world to enhance it [6]. In this technology, the physical and virtual worlds are spatially combined [7]. Thus, the result is a layer of digital artefacts spatially projected and mediated by tools like smartphones, tablets, glasses, contact lenses, or other transparent surfaces [8]. However, MR is sometimes called an advanced AR iteration because the physical environment interacts with projected digital data in real-time [9].

Table 1. Differences between VR, AR, and MR.

Aspect	VR	AR	MR
Definition	A fully immersive digital environment that replaces the real world.	An enhanced version of the real world with digital overlays.	A blend of physical and digital worlds, creating interactive environments where digital and physical objects coexist.
Technology	Uses head-mounted displays (HMDs), sensors, and controllers to create an immersive experience.	Uses cameras, sensors, and displays to overlay digital information onto the real world.	Uses advanced sensors, optics, and processing to integrate virtual content into the real world seamlessly.
UX	Complete immersion in a digital environment, isolated from the real world.	Combines real and virtual worlds, allowing users to see and interact with both.	Seamlessly blends real and VEs, with objects from both interacting in real time.
Devices	VR headsets (e.g., Oculus Rift, HTC VIVE), gloves, and motion-tracking systems.	Smartphones, tablets, AR glasses (e.g., Microsoft HoloLens (Redmond, WA, USA), Google Glass (Ann Arbor, MI, USA)).	MR headsets (e.g., Microsoft HoloLens 2 (Redmond, WA, USA), Magic Leap (Plantation, FL, USA)), specialized controllers.
Applications	Gaming, simulations, training, virtual tours.	Navigation, education, retail, marketing.	Complex simulations, advanced training, design, and collaboration.
Interactivity	High level of interactivity with virtual objects and environments.	Moderate interactivity with digital content overlaid on the real world.	High level of interactivity, with digital and physical objects interacting in real time.

shows more differences between these concepts in terms of definition, technology, user experience (UX), devices, applications, and interactivity.

Recently, the concept of the metaverse has appeared in an applied, clear, and explicit form. It is a VE that has developed from significant advancements in ICT, particularly from VR and internet technology. The term “metaverse” is formed from merging the prefix “meta-”, which indicates transcendence, with the word “universe”. This environment refers to a hypothetical synthetic setting connected to the real world [10]. Neil Stevenson initially coined the term “metaverse” in his speculative fiction novel, Snow Crash, in 1992 [11,12]. In this novel, Stevenson defines the metaverse as an expansive virtual realm that runs similarly to the real world, enabling users to engage with one another through digital avatars.

The metaverse industry has witnessed significant expansion due to the advancements in ICT and changes in the socio-cultural environment, particularly in reaction to the COVID-19 pandemic [13]. Additionally, it can be noted that recently, the private sector has been avid in developing, designing, operating, and planning metaverse platforms [14]. According to [15], the worldwide metaverse market was expected to be valued at USD 65.5 billion in 2022. By 2023, the projected amount is estimated to increase to USD 82 billion, and it is projected to rapidly escalate to USD 936.6 billion by 2030. The shift to a setting where face-to-face interactions are not required has hastened the development of a new standard way of life and the age of consumer culture. Therefore, many global companies and brands are evaluating the metaverse’s possibilities for their future business models, especially considering the growing popularity of smart mobile devices and applications [14,16]. In addition, the transition to a non-face-to-face setting has accelerated the emergence of a new normal lifestyle and consumer culture age.

Metaverses are emerging interfaces intended to facilitate many forms of human–computer interaction (HCI). This novel idea utilizes modern technologies such as AR, mirror worlds, virtual worlds, and lifelogging. Nevertheless, the widespread implementation of this technology has not yet occurred, and it lacks widely recognized standards that align with prevalent digital behaviors in areas such as work, education, business, and entertainment [17].

In the world of software development, developers often encounter numerous challenges and obstacles while designing their VR apps [18]. The development and design of user interfaces (UIs) are considered among these challenges. The UI refers to how a device and a user communicate, including all the methods and processes used to control the device, manipulate its data, and access its contents. When developing VR apps, one of the common challenges and obstacles is the creation and design of VR settings [18,19]. Hence, an effective design is essential for facilitating the clear and accurate delivery of information.

Moreover, individuals will be attracted to the offerings due to their aesthetic design [18]. As we venture into this unexplored realm, UI design plays a crucial role in influencing UX in the metaverse. In the metaverse, users interact with more than just screen-based interactions; they move into a new realm of complete immersion. Therefore, the UI design should provide a seamless transition between the physical and digital realms. Hence, designers must consider the extent of engagement, ensuring that users can easily interact with the dynamic environment of the metaverse.

Notably, virtual worlds have been researched since the mid-nineteen-sixties; thus, many researchers have worked on this topic, and the scientific research community has addressed it in several ways. It is noteworthy that there is a large body of research on the subject of the metaverse, since it is a fertile environment for scientific research. However, a large amount of this research focused on specific aspects of this technology and drove investment in it on this basis [14]. Furthermore, it has also been found through this research that there is a gap in the focus on examining metaverse platforms and studying user behavior within these platforms [14]. Therefore, it can be noted that there is a lack of established criteria for evaluating and analyzing the usability of metaverse platforms, which are widely used by young people, who are particularly attuned to the common terminology, actions, and preferences of their peer group [17]. Therefore, this research aims to narrow this gap by developing usability heuristics to improve the UX in the metaverse. The remainder of this paper is structured as follows: The Usability of Metaverse section presents the popular usability models and attributes, and it discusses the importance of usability heuristics for the metaverse due to several unique characteristics of metaverse environments that distinguish them from traditional digital interfaces. The Methodology and Results section discusses the methodology employed in compiling the new usability heuristics for the metaverse UIs. The Evaluation Model section presents a structured and methodical approach to assess the adequacy of the identified heuristics and sub-heuristics. This is followed by the Conclusion, the acknowledgements, and a list of references.

2. Usability of Metaverse

Various usability models exist, including those developed by researchers like Jakob Nielsen [20], and standardizations such as ISO (9241 [21], 13407 [22], 9126 [23], 14598 [24]) and IEEE (Std.610.12-1990) [25]. Nielsen and ISO-9241-11 models are widely recognized in the usability community. Usability can be evaluated by empirical or analytical methodologies, metrics, and procedures. The empirical approaches aim to discover usability issues by monitoring actual users, whereas the analytical approaches employ inspection procedures undertaken by experts to examine interfaces [26].

Jakob Nielsen is a prominent pioneer and recognized expert on usability for UI design. According to Nielsen, “Usability is a quality attribute that assesses how easy user interfaces are to use. The word usability also refers to methods for improving ease-of-use during the design process” [27]. Thus, Nielsen identified five quality components of usability: learnability, efficiency, memorability, errors, and satisfaction.

Learnability refers to how user-friendly the design is for first-time users in completing fundamental tasks.

Efficiency determines how quickly users can complete activities once they have mastered the design.

Memorability refers to the extent to which users can restore their expertise in the design after they have been away from it for a period of time.

Error indicates the number of errors that users make, the severity of these errors, and the ease with which they may recover from these errors, which are all important questions.

Satisfaction refers to the degree to which the use of the system is satisfying.

As far as usability is concerned, a well-designed UI influences learning time, performance speed, error prevention, and user satisfaction, all of which are important aspects in deciding the success of a product or service overall [14]. A usability evaluation aims to find out how to enhance a product or service’s design while enhancing the UX [28]. Researchers in UX developed many methodological methods to evaluate and identify the usability of products and systems, such as general user tests and heuristic evaluation methods [29]. A general user test is performed by asking a real user to perform a task. In a heuristic evaluation, an expert is the subject of the assessment and conducts the assessment based on usability criteria [30].

Heuristic evaluation was developed by Molich and Nielsen [31] and is considered one of the prominent methods of usability examination [26,32]. This method aims to detect weaknesses in the design of a UI. Thus, it gained popularity in the early 1990s. Due to its cost-effectiveness and intuitive nature, it is easy to motivate individuals to engage in it, it does not need advanced planning, and it can be used at the early stage of the development process [31]. In addition, it is considered an informal usability analysis approach, which is used to identify usability issues in a UI with precision [31]. Furthermore, usability experts conduct this assessment approach in small groups of 3–5 evaluators, following specific guidelines as checklists. Heuristic evaluation can be performed with the use of the following [33,34]:

Heuristic rules, in which the evaluators identify possible usability issues by assessing a system based on a set of rules.

Subjective judgment, in which evaluators rely on their expertise from past usability evaluations to identify usability issues.

Task-based assessment, in which evaluators analyze the execution of tasks in the system and identify any encountered usability issues.

This evaluation method is often conducted by evaluators who assess important tasks, with each task representing a potential set of user interactions with a system or product. During the assessment process, the evaluator compares the different stages of the job to a predetermined set of usability principles, known as heuristics. Professional evaluators employ heuristic evaluation in UX design to methodically assess the usability of a design or product. Through this process, evaluators can identify challenges that may have been neglected by design teams [30]. Nielsen proposed ten usability heuristics for UI design, as follows: the visibility of the system status; the match between the system and the real world; user control and freedom; consistency and standards; error prevention; recognition rather than recall; flexibility and efficiency of use; aesthetic and minimalist design; help for users to recognize, diagnose, and recover from errors; and help and documentation [20].

Although heuristic evaluation was created in the era of desktop computers, the basic method is still useful today. This is because analysts can change the list of heuristics they use during their studies [35]. UX studies in the context of the metaverse have not extensively explored metaverse topics, particularly in terms of analyzing the usability and effectiveness of using the environment and content [14]. This is because the previous research, in the late 2000s, primarily categorized metaverse platforms based on content purpose and production intention, leading to the widespread use of this categorization [36,37]. Joyce states that the implementation of Jakob Nielsen’s ten usability heuristics can enhance the UX of VR apps [38]. However, evaluating VR apps using this assessment approach is still not unusual [18]. Therefore, developing specific usability heuristics for the metaverse is essential due to several unique characteristics of metaverse environments that distinguish them from traditional digital interfaces. The following are the main reasons why specific usability heuristics are required for metaverse environments:

• Three-dimensional interaction: Metaverse UIs differ from standard two-dimensional UIs by requiring navigation and interaction in a 3D environment. Therefore, a specific heuristics set is needed to consider spatial navigation, depth perception, and object manipulation in a 3D environment.
• Immersive experience: The metaverse aims to offer an immersive experience with VR, AR, and MR technology. Therefore, usability heuristics must ensure that these interactions are easy to use, are pleasant, and do not lead to discomfort or confusion for users.
• Social interaction: The metaverse is fundamentally social, facilitating interactions among several users in shared environments. Therefore, usability heuristics should provide instructions for designing social interactions, managing communities, and moderating content created by users to promote pleasant and engaging social experiences.
• Integration of digital and physical worlds: The metaverse aims to blend digital and physical worlds. Therefore, this requires heuristics that are intended to assist in creating smooth experiences in both domains. This involves integrating IoT devices, real-world data, and physical activities into the digital experience.
• Economic transactions: The metaverse’s economy relies on virtual products, services, and real estate. Therefore, usability heuristics must focus on enhancing the UX associated with financial transactions by ensuring they are safe, transparent, and user-friendly.
• Accessibility and inclusivity: establishing heuristics in the metaverse is essential to guarantee accessibility and inclusivity for users with various skills, preferences, and cultural backgrounds because of its extensive and diverse audience.
• Ethical and privacy considerations: The immersive and ubiquitous nature of the metaverse creates serious ethical and security issues. Therefore, usability heuristics should contain guidelines for protecting user privacy, ensuring ethical interactions, and promoting trust and safety in the metaverse.

Consequently, specific usability heuristics for the metaverse are required to assist designers and developers in creating environments that are not only impressive, but also user-friendly, engaging, and inclusive. In addition, these heuristics can serve as a foundation for developing best practices in the design and management of metaverse experiences and ensuring they meet the needs and expectations of a wide range of users.

3. Methodology and Results

Four steps, which were adapted from [32], were followed consecutively, as can be seen from Figure 1, to develop usability heuristics and guidelines that concentrate on UIs of the metaverse, for the context of this research. This is due to the large intersections and common characteristics between the mobile UIs and the metaverse UIs, such as user-centric design, touch and gesture controls, adaptive and responsive design, contextual awareness, voice and audio interaction, multitasking capabilities, social and collaborative features, user feedback, and iterative Improvements.

Step 1. 

Defining the problem scope to categorize and identify the distinctive characteristics of metaverse interaction and the usability issues related to its UIs.

Step 2. 

Analyzing and enriching the existing usability heuristics and organizing them into a new list tailored for the metaverse environment. The generated list was based on metaverse usability research published in the literature. Thus, the newly generated heuristics list represents the abstract concept of usability criteria.

Step 3. 

Sub-heuristics were added to the existing list to provide more explanation of the abstract heuristics generated in step 2 and to maintain the usability of the application’s UI, as well as metaverse UIs.

Step 4. 

Standardization of the editing and format of the new list to enhance its accessibility for non-expert people.

Step 1. 

Problem Scope Definition

The UIs of the metaverse are distinct from those of traditional apps due to the unique characteristics and needs of immersive, 3D virtual worlds. The following are the main reasons behind these variations:

• Dimensionality: Traditional apps usually work in 2D spaces with flat screens and straightforward navigation. On the other hand, the metaverse operates in a 3D world, requiring interfaces that help users move around and interact within a more complex spatial environment.
• Immersive interaction: Traditional apps use familiar input devices like keyboards, mice, or touchscreens. In contrast, metaverse interfaces use more immersive methods, such as VR helmets, motion controllers, haptic devices, and voice commands, which enhance the user’s sense of immersion and presence in the virtual world.
• Social presence: The metaverse is focused on socializing and working together, allowing users to interact in real time within a shared space. To support this, metaverse interfaces need to facilitate these interactions through avatars, voice chats, gestures, and shared experiences. This is quite different from the more isolated or asynchronous interactions we usually see in traditional apps.
• Customization and personalization: The metaverse allows users to customize and personalize almost everything, from their appearance and surroundings to the physics of virtual worlds. Therefore, UIs need to be designed to make these customizations easy and user-friendly.
• Continuous and persistent worlds: The metaverse stands out from traditional apps because its worlds continue to exist and evolve even when users are not online. Therefore, UI designs need to clearly inform users about what happened while they were away and help them re-engage with the environment seamlessly.
• Complex economies and transactions: The metaverse supports complex economies where users can buy, sell, and trade virtual products, assets, and services. Because of this, UI components need to make these transactions easy and user-friendly, including features like marketplaces, auction houses, and inventory management systems.
• Ethical and privacy concerns: Because the metaverse is so immersive and all-encompassing, its UIs need to be more robust to handle privacy, security, and ethical concerns. This means having clear consent processes, privacy settings, and ways to report or prevent harassment and abuse.
• Accessibility: It is important to make sure the metaverse is accessible to everyone, regardless of their abilities. This means integrating accessibility features into metaverse UIs from the start to support users with visual, auditory, motor, or cognitive limitations, which often have not been fully addressed in traditional applications.

Consequently, developing UIs for the metaverse involves reevaluating user interaction paradigms to address the distinct problems and challenges posed by immersion in three-dimensional environments. Since the metaverse is considered an expansive virtual space encompassing a variety of interconnected, immersive, digital environments, it presents several usability challenges for its UIs. These challenges stem from the metaverse’s ambition to provide a seamless, intuitive, and engaging experience across diverse platforms, activities, and user demographics. However, numerous studies have been reviewed to compile the potential usability challenges for metaverse UIs, such as [3,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53]. Thus,

Table 2. Compiled usability challenges with their descriptions.

Category	Usability Challenge	Description
Complexity and Overload	Information Overload	The vast amount of information and interactive elements in the metaverse can overwhelm users, making it difficult to focus on tasks and absorb necessary information.
	Navigational and Orientational Complexity	Navigating 3D spaces can be more complex than 2D interfaces, leading to user frustration and confusion.
Interaction Design	Control Mechanisms	Traditional input devices (mouse, keyboard) may not translate well to 3D environments. New interaction paradigms like VR controllers, hand tracking, and gestures need to be intuitive.
	Latency and Responsiveness	Delays in system response can significantly impact the user experience, causing motion sickness and frustration.
	Interaction and Manipulation of Virtual Objects	Interacting with and manipulating objects in a virtual space can be less intuitive than in the real world, leading to inefficiency and user frustration.
User Adaptation	Learning Curve	Users often face a steep learning curve with new interaction methods and navigational paradigms.
	Customization	The need for customizable interfaces to fit diverse user needs and preferences is crucial, but often lacking.
	Avatar Representation and Customization	Creating and managing avatars that accurately represent users can be complex, impacting user satisfaction and engagement. Additionally, the customization process needs to be intuitive and flexible.
Accessibility	Inclusivity	Ensuring accessibility for users with disabilities is a significant challenge. This includes visual, auditory, and motor impairments.
	Ergonomics	Prolonged use of VR headsets and other devices can cause physical discomfort and health issues.
Social Interaction	Presence and Embodiment	Creating a sense of presence and realistic avatars is challenging, impacting social interactions.
	Privacy, Security, and Ethical Issues	Managing privacy and security within VEs, especially in social interactions, is a critical concern. In addition, ethical issues, such as identity theft and harassment, pose significant challenges.
Technological Constraints	System Performance and Hardware Limitations	Current hardware may not fully support the immersive experiences users expect.
	Connectivity Issues	Reliable and high-speed internet connections are essential for a seamless experience, which can be a limiting factor.
Content Creation and Management	User-Generated Content	Managing and moderating user-generated content in a vast and dynamic environment is challenging.
	Content Quality	Ensuring high-quality and relevant content that engages users while being usable is essential
	Realism vs. Abstraction	Balancing realism and abstraction in VEs to ensure immersion without overwhelming the user or causing a sensory overload.

demonstrates the compiled usability challenges with their descriptions.

Step 2. 

Usability Heuristics for Metaverse

Nielsen’s ten usability heuristics are broad principles for UI design aimed at serving as a comprehensive framework for enhancing user experience and usability in design [20]. However, these heuristics were initially developed for PCs. Murtza, Monroe, and Youmans presented a novel set of heuristics designed for conducting usability inspections of VR systems using the Heuristic Evaluation method [35]. These heuristics were developed to identify usability issues in both emerging and existing VR hardware and software. Their approach involved surveying VR users and analyzing their responses to identify nine categories of common usability problems in VR systems. The resulting heuristics provide a valuable resource for UX researchers aiming to employ Heuristic Review to evaluate VR products. Mohammad and Pedersen highlight that five essential elements for UX in the VR learning context have been identified in the literature, as follows: embodiment, empathy, flow, immersion, and presence [30]. Sutcliffe and Gault introduced twelve heuristics specifically for assessing VE UIs [54]. Their approach builds on Nielsen’s usability heuristics, incorporating additional principles tailored to VEs, as suggested by Sutcliffe and Kaur [55]. Endsley and others developed a set of design heuristics specifically for AR to enhance AR design practices. Their goal was to support human factors, ergonomics, and UX professionals in the growing AR community [56]. Rusu and others proposed a set of 16 specific usability heuristics, along with a 49-item usability checklist, to aid in evaluating the usability of virtual world applications [57]. Therefore, all these heuristics were compiled together and formed a new metaverse-specific usability heuristics list that contains 52 heuristics, as can be seen in

Table 3. Usability heuristics, sub-heuristics, and checklist for metaverse UIs.

#	Heuristic	Description	Sub-Heuristics	Proposed Checklist
1	Visibility of system status [20]	“The design should always keep users informed about what is going on, through appropriate feedback within a reasonable amount of time.” “A VW interface should keep user informed on both avatar’s state, and the relevant facts and events that affect him.” [57]	Provide immediate feedback for user actions. Display loading indicators for ongoing processes. Use status bars or notifications to show progress.	Is the current system status clearly displayed to users? Are users informed about what is happening through appropriate feedback within a reasonable time? Are notifications or updates about changes in the system state easily noticeable?
2	Match between system and the real world [20]	“The design should speak the users’ language. Use words, phrases, and concepts familiar to the user, rather than internal jargon. Follow real-world conventions, making information appear in a natural and logical order.”	Use familiar symbols and icons. Apply real-world metaphors in the interface design. Ensure natural and realistic interactions.	Does the system use concepts and language familiar to the user? Are visual elements and interactions consistent with real-world expectations? Is the user interface intuitive and easy to understand?
3	User control and freedom [20]	“Users often perform actions by mistake. They need a clearly marked “emergency exit” to leave the unwanted action without having to go through an extended process.”	Offer undo and redo options. Provide easy access to exit points or emergency stops. Allow users to customize their interactions and settings.	Can users easily undo and redo actions? Are emergency exits clearly marked and accessible? Do users have the ability to control their interactions and movements within the system?
4	Consistency and standards [20]	“Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform and industry conventions.” “A VW should be consistent in using language and concepts. Avatar’s actions and their effects on the VW’s environment should be coherent and consistent. User—avatar, as well as avatar—VW’s objects, should be consistent.” [57]	Maintain consistent design elements throughout the interface. Adhere to platform-specific conventions. Use uniform terminology and iconography.	Are design elements and interactions consistent throughout the system? Are established conventions and standards being followed? Is the terminology used consistently across the interface?
5	Error prevention [20]	“Good error messages are important, but the best designs carefully prevent problems from occurring in the first place. Either eliminate error-prone conditions, or check for them and present users with a confirmation option before they commit to the action.” “A VW should prevent users from performing actions that could lead to errors, and should avoid confusions that could lead to mistakes, during user –control panel interaction, as well as during (user’s) avatar –VW interaction.” [57]	Implement validation checks before user actions. Provide warnings for potentially harmful actions. Design workflows to minimize the risk of errors.	Are potential errors anticipated and prevented before they occur? Are users warned of possible errors before they commit to an action? Are there measures in place to reduce the likelihood of errors?
6	Recognition rather than recall [20]	“Minimize the user’s memory load by making elements, actions, and options visible. The user should not have to remember information from one part of the interface to another. Information required to use the design (e.g., field labels or menu items) should be visible or easily retrievable when needed.” Clarity: “A VW should offer an easy to understand user control panel, using clear graphic elements, text and language, grouping elements by their purposes, and offering easy access to the main functionality.” [57] “A VW should maintain main objects, options, elements and actions always available or easy to get to. It should provide ways to mark and remember places already visited and/or of user’s interest.” [57]	Make options and actions visible. Provide clear instructions and cues at the point of need. Use visual aids to reduce memory load.	Are objects, actions, and options visible so that the user does not have to remember information? Are instructions and cues provided at the point of need? Is the interface designed to minimize memory load on the user?
7	Flexibility and efficiency of use [20]	“Shortcuts—hidden from novice users—may speed up the interaction for the expert user so that the design can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.” “A VW should provide customizable shortcuts, abbreviations, accessibility keys or command lines. The user interface/control panel should be customizable.” [57]. Simplicity “A VW should provide easy and intuitive interaction with the environment’s virtual objects. Only relevant information should be given, in order to avoid the control panel’s overload” [57].	Offer shortcuts and advanced options for experienced users. Enable users to personalize their interface. Provide multiple ways to accomplish tasks.	Are there shortcuts or accelerators available for experienced users? Can users customize the interface to suit their needs? Is the system efficient for both novice and expert users?
8	Aesthetic and minimalist design [20]	“Interfaces should not contain information that is irrelevant or rarely needed. Every extra unit of information in an interface competes with the relevant units of information and diminishes their relative visibility.”	Avoid clutter and unnecessary elements. Use a clean and simple visual design. Focus on the essential features and information.	Is the design visually appealing and free of unnecessary elements? Is the information presented simply and clearly? Are distractions minimized in the user interface?
9	Help users recognize, diagnose, and recover from errors [20]	“Error messages should be expressed in plain language (no error codes), precisely indicate the problem, and constructively suggest a solution.” “A VW should provide user appropriate mechanisms to recover from errors, and exit ways from unwanted situations. It should include clear messages, hopefully indicating causes and solutions for errors.” [57]	Display clear and concise error messages. Offer suggestions for correcting errors. Provide step-by-step guides for troubleshooting.	Are error messages clear and easy to understand? Are suggestions provided to help users recover from errors? Is help available to guide users through error resolution?
10	Help and documentation [20]	“It’s best if the system doesn’t need any additional explanation. However, it may be necessary to provide documentation to help users understand how to complete their tasks.” “A VW should provide an easy to find, easy to understand, and complete online documentation, accessible from both inside and outside of the world itself” [57].	Ensure help documentation is easily accessible. Offer contextual help within the interface. Provide comprehensive guides and tutorials.	Is help documentation easily accessible and searchable? Are instructions provided concise and relevant to the user’s task? Is there in-context help available within the user interface?
11	Synchronous body movements [35]	“The system and interface should stay in synchrony with human head and body movements in real time to prevent lag.”	Ensure accurate tracking of user movements. Minimize latency between action and response. Provide natural and intuitive motion controls.	Does the system accurately track and respond to the user’s body movements? Is there a noticeable lag between the user’s actions and the system’s response? Are movements in the VE natural and fluid?
12	physical space constraints [35]	“System designers should try to account for the real-world physical space users will occupy when interacting with the system.”	Design interactions to fit within users’ physical spaces. Warn users of potential collisions or obstacles. Ensure safe movement within the VE	Does the system account for the user’s physical space limitations? Are users warned of potential physical obstacles in their real environment? Is there sufficient space for users to interact safely?
13	Immersion [35]	“The system should immerse the user in VR, specific to visual realism.”	Use high-quality visuals and sounds to enhance immersion. Minimize distractions from the VE. Create a seamless and engaging user experience.	Does the system provide a highly immersive experience? Are visual and auditory elements realistic and engaging? Is the sense of presence in the VE strong?
14	Glitchiness [35]	“The system should promote a streamlined experience by keeping systematic glitches low.”	Ensure the system is stable and reliable. Minimize bugs and performance issues. Provide smooth and uninterrupted interactions.	Are there frequent glitches or bugs in the system? Is the system stable and reliable during use? Are performance issues minimized to prevent disruptions?
15	Minimize switching between actual and virtual world [35]	“The system should be able to rely on itself for all usage; that is, keep all necessary user tasks and information within VR, instead of creating tasks that the user may only be able to execute when VR headset is taken off or information that can only be accessed by taking headset off.”	Keep necessary information within the VE. Reduce the need for users to remove their headset. Design tasks that can be completed entirely in VR.	Can users complete tasks without frequently switching between the real and virtual worlds? Is necessary information accessible within the VE? Are interruptions minimized during the virtual experience?
16	Cord design [35]	“The cord of the system should be designed such that VR usage requires minimal maintenance, e.g., providing adequate length and mobility to keep entanglement to a minimum.”	Ensure cords are long enough for freedom of movement. Design cords to minimize entanglement risks. Use wireless options where possible.	Are the cords and cables designed to be user-friendly? Are cords long enough to provide flexibility without being tripping hazards? Are cords organized to avoid entanglement?
17	Headset comfort [35]	“The headset of the system should be designed to be comfortable for prolonged wear.”	Design headsets to be lightweight and ergonomic. Provide adjustable straps and padding for comfort. Ensure the headset fits securely without causing discomfort.	Is the headset comfortable to wear for extended periods? Is the weight of the headset evenly distributed? Are adjustments available to fit different head sizes?
18	Mental comfort [35]	“The system should be designed to prevent sensations of physical illness during use, by preventing jarring movement lag, increasing realism of visuals, and so on.”	Avoid inducing motion sickness or discomfort. Use smooth and realistic motion effects. Provide options to adjust the visual and auditory settings.	Does the system avoid causing motion sickness or discomfort? Are visual and auditory stimuli balanced to prevent sensory overload? Is the experience designed to be mentally engaging without being overwhelming?
19	User interface design [35]	“The system’s interface and hardware controls should have a intuitive design and navigation, adhering to usability conventions.”	Ensure the interface is intuitive and easy to navigate. Use clear and consistent design elements. Provide a visual hierarchy to guide user attention.	Is the user interface intuitive and easy to navigate? Are interactive elements clearly identifiable and responsive? Is the layout of the interface logical and user-friendly?
20	Embodiment [30] (p. 9), [58,59,60,61]	“A core concept in VR that often refers to the experienced embodiment a user feels in a VE; ultimately generates a sense of presence in the virtual world. Experienced embodiment aids the user in feeling as if they are a part of the VE and feel connected to the other agents in the world.”	Create realistic avatars or representations of the user. Ensure the user feels a sense of presence in their virtual body. Provide responsive and natural interactions.	Do users feel a sense of embodiment within the VE? Are avatars or representations of the user realistic and responsive? Is the user’s presence in the virtual world convincingly portrayed?
21	Empathy [30] (p. 9), [61]	“Being in the same space as another character makes the user strongly feel the character’s emotion in a situation. Users may view a VR experience as more realistic and compassionate as a result of simulated empathy in VR.”	Design interactions that promote understanding and connection. Include elements that foster emotional engagement. Provide tools for expressing and sharing emotions.	Does the system facilitate empathy between users or with virtual characters? Are interactions designed to be emotionally engaging? Is there a sense of connection and understanding in social interactions?
22	Flow [30] (p. 9), [61]	“The state in which the user is engaged in the task at hand; flow can be an experience of immersion into a certain user action. Users may experience flow when the task at hand is engaging and challenges the user to utilize their skills fully.”	Create a seamless and engaging user experience. Ensure tasks are challenging but achievable. Provide immediate feedback to maintain user momentum.	Does the system support a state of flow where users are fully engaged and focused? Are tasks challenging but achievable, promoting continuous involvement? Is feedback provided to maintain the user’s momentum?
23	Immersion [30] (p. 9), [58,61,62,63,64]	“An ambiguous term, often used synonymously with presence, though the literature states that it could be either the level of fidelity of the VE or the feeling the user has while immersed in the environment.”	Use realistic and high-quality sensory inputs. Minimize interruptions and distractions. Create an engaging and believable VE.	Are the sensory inputs (visual, auditory, tactile) effectively combined to enhance immersion? Is the VE convincingly realistic? Are users able to lose themselves in the virtual experience?
24	Presence [30] (p. 9), [58,62,64]	“Generally refers to the user’s experience in the virtual world and how they act and react as if they are physically there.”	Enhance the sense of being physically present in the VE. Use realistic interactions and feedback. Minimize factors that break the sense of presence.	Do users feel like they are truly “present” in the VE? Is the sense of presence maintained throughout the interaction? Are distractions minimized to enhance the feeling of presence?
25	Natural engagement [54]	“Interaction should approach the user’s expectation of interaction in the real world as far as possible. Ideally, the user should be unaware that the reality is virtual. Interpreting this heuristic will depend on the naturalness requirement and the user’s sense of presence and engagement.”	Ensure interactions feel natural and intuitive. Use familiar and intuitive controls. Design engaging and immersive experiences.	Are interactions within the VE natural and intuitive? Do users feel naturally engaged with the system? Is the interaction design seamless and unobtrusive?
26	Compatibility with the user’s task and domain [54]	“The VE and behaviour of objects should correspond as closely as possible to the user’s expectation of real world objects; their behaviour; and affordances for task action.”	Tailor the system to specific tasks and user needs. Ensure functionalities are relevant and useful. Adapt the interface to different contexts and user goals.	Is the system tailored to the specific tasks and domain of the user? Are functionalities relevant and useful for the user’s goals? Is the system adaptable to different user contexts and needs?
27	Natural expression of action [54]	“The representation of the self/presence in the VE should allow the user to act and explore in a natural manner and not restrict normal physical actions. This design quality may be limited by the available devices. If haptic feedback is absent, natural expression inevitably suffers.”	Enable users to express actions naturally and intuitively. Provide immediate and appropriate responses to user actions. Ensure interactions are fluid and seamless.	Are actions within the VE naturally expressed? Do users feel a sense of control over their actions? Is the response to user actions immediate and appropriate?
28	Close coordination of action and representation [54]	“The representation of the self/presence and behaviour manifest in the VE should be faithful to the user’s actions. Response time between user movement and update of the VE display should be less than 200 ms to avoid motion sickness problems.”	Synchronize user actions with visual representations. Ensure accurate and immediate feedback. Minimize latency and discrepancies.	Are user actions closely coordinated with visual representations? Is there a seamless connection between user input and system output? Are movements and interactions accurately mirrored in the VE?
29	Realistic feedback [54]	“The effect of the user’s actions on virtual world objects should be immediately visible and conform to the laws of physics and the user’s perceptual expectations.”	Provide realistic and informative feedback. Ensure feedback is immediate and contextually relevant. Use visual, auditory, and tactile cues effectively.	Is feedback from the system realistic and informative? Are users provided with immediate and appropriate responses to their actions? Is feedback designed to enhance the user’s understanding of the VE?
30	Faithful viewpoints [54]	“The visual representation of the virtual world should map to the user’s normal perception, and the viewpoint change by head movement should be rendered without delay.”	Ensure viewpoints are consistent and realistic. Provide accurate camera angles and perspectives. Ensure the visual representation matches the user’s expectations.	Are the viewpoints within the VE realistic and consistent? Do camera angles and perspectives accurately reflect the user’s position and movements? Is the visual representation of the environment faithful to the user’s expectations?
31	Navigation and orientation support [54]	“The users should always be able to find where they are in the VE and return to known, preset positions. Unnatural actions such as fly-through surfaces may help but these have to be judged in a trade-off with naturalness (see heuristics 1 and 2).”	Provide clear navigation aids and orientation cues. Ensure users can easily find their way within the VE. Use maps, compasses, and guides to support navigation.	Is navigation within the VE intuitive and easy? Are users provided with clear orientation cues? Is there support for users to easily find their way within the environment?
32	Clear entry and exit points [54]	“The means of entering and exiting from a virtual world should be clearly communicated.”	Clearly mark entry and exit points within the VE. Ensure smooth transitions between areas. Provide clear instructions for entering and leaving the environment.	Are entry and exit points within the VE clearly marked? Can users easily enter and leave different sections of the environment? Are transitions between areas smooth and understandable?
33	Consistent departures [54]	“When design compromises are used they should be consistent and clearly marked, e.g., cross-modal substitution and power actions for navigation.”	Ensure departures from the VE are predictable. Provide clear processes for ending the virtual experience. Ensure users understand how to exit the environment.	Are departures from the VE consistent and predictable? Do users understand how to exit VE? Is there a clear and consistent process for ending the virtual environment?
34	Support for learning [54]	“Active objects should be cued and if necessary explain themselves to promote learning of VEs.”	Provide adequate support for learning and skill development. Offer tutorials and instructional materials. Ensure the learning process is intuitive and engaging.	Does the system provide adequate support for learning and skill development? Are instructional materials and tutorials available and accessible? Is the learning curve manageable for new users?
35	Clear turn-taking [54]	“Where system initiative is used it should be clearly signaled and conventions established for turn-taking.”	Ensure turn-taking in multi-user interactions is clear and fair. Provide mechanisms to manage turn-taking smoothly. Ensure users understand when it is their turn to interact.	Is turn-taking in multi-user interactions clear and fair? Are there mechanisms to manage turn-taking smoothly? Do users understand when it is their turn to interact?
36	Sense of presence [54]	“The user’s perception of engagement and being in a ‘real’ world should be as natural as possible.”	Maintain a strong sense of presence throughout the experience. Ensure users feel physically and emotionally present. Minimize factors that break the sense of presence.	Is the sense of presence strong and consistent throughout the experience? Do users feel like they are physically in the VE? Is the virtual presence maintained even during complex interactions?
37	Fit with user environment and task [54]	“AR experiences should use visualizations and metaphors that have meaning within the physical and task environment in which they are presented. The choice of visualizations & metaphors should match the mental models that the user will have based on their physical environment and task.”	Design the VE to fit the user’s physical and task-related needs. Ensure tools and interfaces align with user objectives. Adapt the environment to different tasks and scenarios.	Is the VE designed to fit the user’s physical and task-related needs? Are tools and interfaces aligned with the user’s objectives? Is the environment adaptable to different tasks and scenarios?
38	Form communicates function [56]	“The form of a virtual element should rely on existing metaphors that the user will know in order to communicate affordances and capabilities.”	Ensure the design clearly communicates the function of each element. Use visual design to indicate the purpose of tools and features. Ensure users understand the functionality at a glance.	Does the design clearly communicate the function of each element? Are users able to understand the purpose of tools and features at a glance? Is the visual design aligned with the functionality?
39	Minimize distraction and overload [56]	“AR experiences can easily become visually overwhelming. Designs should work to minimize accidental distraction due to designs that are overly cluttered, busy, and/or movement filled.”	Minimize distractions to maintain user focus. Present information in a clear and concise manner. Avoid cognitive overload by removing unnecessary elements.	Are distractions minimized to maintain focus on the task? Is information presented in a way that avoids cognitive overload? Are unnecessary elements removed to enhance clarity?
40	Adaptation to user position and motion [56]	“The system should adapt such that virtual elements are useful and usable from the variety of viewing angles, distances, and movements that will be taken by the user.”	Ensure the system adapts to the user’s physical position and movements. Design interactions to accommodate different postures and motions. Ensure the VE is responsive to changes in user position.	Does the system adapt to the user’s physical position and movements? Are interactions designed to accommodate different postures and motions? Is the VE responsive to changes in the user’s position?
41	Alignment of physical and virtual worlds [56]	“Placement of virtual elements should make sense in the physical environment. If virtual elements are aligned with physical objects, this alignment should be continuous over time and viewing perspectives.”	Align physical and virtual elements to prevent confusion. Ensure the VE corresponds accurately to the user’s physical space. Design interactions to seamlessly integrate both worlds.	Are physical and virtual elements well aligned to prevent confusion? Does the VE correspond accurately to the user’s physical space? Are interactions designed to seamlessly integrate both worlds?
42	Fit with user’s physical abilities [56]	“Interaction with AR experiences should not require the user to perform actions that are physically challenging, dangerous, or that require excess amounts of coordination. All physical motion required should be easy.”	Ensure the system is accessible to users with different physical abilities. Design controls and interfaces to be user-friendly for all users. Provide accommodations for users with physical limitations.	Is the system accessible to users with different physical abilities? Are controls and interfaces designed to be user-friendly for all users? Are there accommodations for users with physical limitations?
43	Fit with user’s perceptual abilities [56]	“AR experiences should not present information in ways that fall outside of an intended user’s perceptual thresholds. Designers should consider size, color, motion, distance, and resolution when designing for AR”	Design the system to cater to users’ perceptual abilities. Optimize visual, auditory, and tactile elements for different users. Provide support for users with perceptual impairments.	Is the system designed to cater to users’ perceptual abilities? Are visual, auditory, and tactile elements optimized for different users? Is there support for users with perceptual impairments?
44	Accessibility of off-screen objects [56]	“Interfaces that require direct manipulation (for example, AR & touch screens) should make it easy for users to find or recall the items they need to manipulate when those items are outside the field of view.”	Ensure off-screen objects are easily accessible and discoverable. Design navigation to ensure all objects are reachable. Provide cues and aids for locating off-screen elements.	Are off-screen objects easily accessible and discoverable? Can users interact with elements that are not immediately visible? Is navigation designed to ensure all objects are reachable?
45	Accounting for hardware capabilities [56]	“AR experiences should be designed to accommodate for the capabilities & limitations of the hardware platform.”	Optimize the system to make full use of available hardware capabilities. Minimize performance issues to ensure a smooth experience. Ensure hardware potential is fully utilized for enhanced interactions.	Does the system make optimal use of available hardware capabilities? Are performance issues minimized to ensure a smooth experience? Is the hardware’s potential fully utilized for enhanced interactions?
46	Visualization [57]	“A VW should give user control over the objects and visual effects that he/she will get visible.”	Ensure visual elements are clear, detailed, and informative. Present information in a visually appealing and understandable manner. Optimize graphics to enhance user experience.	Are visual elements clear, detailed, and informative? Is information presented in a visually appealing and understandable manner? Are graphics optimized to enhance user experience?
47	Avatar’s customization [57]	“A VW should allow fully avatars’ customization.”	Provide options for users to customize their avatars. Ensure customization options are diverse and inclusive. Design the customization process to be intuitive and easy to use.	Can users customize their avatars to reflect their preferences? Are customization options diverse and inclusive? Is the customization process intuitive and easy to use?
48	Orientation and navigation [57]	“A VW should provide full (customizable) information on avatar’s position, paths to a desired destination, and passage ways from one position to another (according to VW’s rules).”	Ensure navigation within the VE is straightforward. Provide clear orientation aids and cues. Design the environment to be easy to navigate and understand.	Is navigation within the VE straightforward? Are users provided with clear orientation aids? Is it easy for users to find their way and understand their location?
49	World interaction [57]	“A VW should clearly indicate the objects that user may interact with, as well as the actions that user may perform over the objects.”	Ensure interactions within the virtual world are natural and engaging. Design interactive elements to be responsive and meaningful. Ensure users can intuitively interact with the environment and objects.	Are interactions within the virtual world natural and engaging? Can users interact with the environment and objects intuitively? Are interactive elements responsive and meaningful?
50	World’s rules [57]	“A VW should clearly indicate its own rules and the rules that govern avatars, especially the actions that are impossible in the real (user’s) world, but are possible in the VW (and vice versa).”	Clearly define and communicate the rules of the virtual world. Ensure users understand what is expected of them. Maintain consistency and logic in the world’s rules.	Are the rules of the virtual world clearly defined and understandable? Do users know what is expected of them within the environment? Are the world’s rules consistent and logical?
51	Communication between avatars [57]	“A VW should allow easy communication among users, through their avatars.”	Ensure communication between avatars is clear and effective. Provide tools and features to facilitate social interactions. Design the communication interface to be user-friendly and intuitive.	Is communication between avatars clear and effective? Are there tools and features to facilitate social interactions? Is the communication interface user-friendly and intuitive?
52	Camera control [57]	“A VW should give user control over camera, allowing a customizable user’s view.”	Ensure camera control is intuitive and responsive. Provide options for users to adjust their viewpoint. Ensure camera movement is smooth and free of glitches.	Is the camera control intuitive and responsive? Can users easily adjust their viewpoint as needed? Is the camera movement smooth and free of glitches?

.

Step 3. 

Sub-Heuristics for the Identified Heuristics

The compiled 52 metaverse-specific usability heuristics were enriched with 156 sub-heuristics, as can be seen from the mind-map diagram elaborated in Figure 2 and described in detail in Table 3. This step is important in order to provide more explanation for the abstract heuristics generated in step 2 and to maintain the usability of the application’s UI, as well as the metaverse UI. The identified sub-heuristics were based on the authors’ experience in the field of the usability heuristics of UIs.

Step 4. 

Usability Checklist for Metaverse UIs

In this step, the compiled sub-heuristics were formatted as a checklist, as can be seen from Table 3, to enhance its accessibility for non-expert people. In addition, this checklist can be used as a tool to evaluate the usability of metaverse UIs.

4. Evaluation Model

In this section, a structured and methodical approach is proposed to assess the adequacy of the identified 52 heuristics and 156 sub-heuristics in Section 3. This approach consists of 7 steps, which are discussed by employing a concrete use case, as follows:

Step 1. 

Case Selection and Objectives Definition: In this step, a concrete metaverse case is selected for a specific metaverse application or environment, such as a virtual classroom, gaming environment, social VR platform, or other. Subsequently, the objectives are defined, and the intended goals and key functionalities of the selected metaverse case are clearly outlined. An example is provided below:

• Case: Virtual Classroom in a Metaverse Environment.
• Objectives: To create a virtual classroom that enhances student engagement, provides realistic interactions, supports diverse learning activities, and ensures accessibility.

Step 2. 

Heuristic Mapping: In this step, each heuristic and sub-heuristic is aligned with the specific objectives and functionalities of the metaverse case. A matrix is created to visualize the coverage of each heuristic in relation to the metaverse’s objectives. In addition, the relevance of heuristics is identified by determining which heuristics are directly applicable to the chosen metaverse case. This means that not all heuristics may be relevant for every scenario.

Table 4. Coverage of identified heuristics in relation to the identified objectives of a virtual classroom case.

#	Heuristic	Engagement	Realistic Interactions	Diverse Learning	Accessibility
1	Visibility of system status	X	X
2	Match between system and the real world		X	X
3	User control and freedom			X	X
4	Consistency and standards	X		X	X
5	Error prevention	X			X
6	Recognition rather than recall			X	X
7	Flexibility and efficiency of use	X		X
8	Aesthetic and minimalist design	X	X
9	Help for users to recognize, diagnose, and recover from errors				X
10	Help and documentation			X	X
11	Synchronous body movements		X
12	Physical space constraints		X
13	Immersion	X	X
14	Glitchiness		X
15	Minimize switching between actual and virtual world		X
16	Cord design		X
17	Headset comfort		X
18	Mental comfort		X
19	User interface design	X		X
20	Embodiment		X
21	Empathy	X	X
22	Flow	X	X	X
23	Immersion	X	X
24	Presence	X	X
25	Natural engagement		X
26	Compatibility with the user’s task and domain		X	X
27	Natural expression of action		X
28	Close coordination of action and representation		X
29	Realistic feedback		X
30	Faithful viewpoints		X
31	Navigation and orientation support		X		X
32	Clear entry and exit points		X
33	Consistent departures
34	Support for learning	X		X	X
35	Clear turn-taking				X
36	Sense of presence	X	X
37	Fit with user environment and task		X
38	Form communicates function		X	X
39	Minimize distraction and overload	X
40	Adaptation to user position and motion		X
41	Alignment of physical and virtual worlds		X
42	Fit with user’s physical abilities				X
43	Fit with user’s perceptual abilities				X
44	Accessibility of off-screen objects				X
45	Accounting for hardware capabilities		X
46	Visualization			X
47	Avatar’s customization			X
48	Orientation and navigation		X		X
49	World interaction		X
50	World’s rules		X
51	Communication between avatars	X	X
52	Camera control		X
	X: covered

presents the coverage of each identified heuristic in relation to the identified objectives of the selected case (Virtual Classroom in a Metaverse Environment) in step 1.

Step 3. 

User Scenario Development: In this step, detailed user scenarios that represent typical interactions and experiences within the metaverse case are required. These should cover a range of activities and user types (novices, experts, users with disabilities, and others). Next, each user scenario is mapped to the relevant heuristics to ensure that all aspects of the UX are considered. The following are some example scenarios:

• Lecture delivery: A teacher delivers a lecture; students can raise their hands, ask questions, and interact with the virtual whiteboard.
• Group discussions: Students form groups to discuss a topic, share virtual notes, and collaborate on a project.
• Hands-on activities: Students participate in a virtual laboratory experiment, manipulating virtual objects and observing outcomes.
• Accessibility features: A student with a disability navigates the virtual classroom using assistive technologies and interacts with content.

Step 4. 

Expert Review and Validation: In this step, a panel of experts in UX, VR, AR, and metaverse design is formulated to conduct a heuristic evaluation of the metaverse case. Thus, the identified heuristics and sub-heuristics in Table 3, and specifically the proposed checklist in that table, can be used in this evaluation. Each expert should independently assess how well each heuristic is addressed in the user scenarios. Next, the feedback on the relevance, clarity, and completeness of each heuristic is collected.

Step 5. 

User Testing: This step starts with developing a prototype of the metaverse case and then conducting usability testing sessions with real users. These testing sessions aim to observe and document the users’ interactions and focus on areas related to the identified heuristics, considering metrics such as time to complete tasks, error rates, user satisfaction scores, and others. Subsequently, the qualitative data are collected through surveys and interviews with the users to obtain their feedback on their experiences and any issues encountered.

Step 6. 

Data Analysis and Reporting: In this step, the expert evaluations are compared with user testing results by using qualitative analysis software for coding interview data and statistical tools for quantitative analysis in order to identify any gaps or discrepancies. This allows the determination of whether the heuristics and sub-heuristics adequately cover the critical aspects of UX for the metaverse case and makes it possible to pay special attention to areas where users encounter difficulties, or where experts have highlighted concerns. At the end, recommendations for refining the heuristics based on the findings are provided, highlighting any additional heuristics or modifications that are needed to suit the metaverse case better.

Step 7. 

Iterative Improvement: This is the final step, which attempts to refine and update the heuristics and sub-heuristics based on the analysis to suit the specific needs of the metaverse case. Subsequently, a follow-up evaluation with refined heuristics is conducted to ensure their effectiveness and adequacy.

By using this concrete use case, the proposed methodology can be thoroughly tested and refined to ensure that the proposed heuristics and sub-heuristics are adequate for creating an effective and engaging virtual classroom environment in the metaverse.

5. Conclusions

The metaverse is a VE that has become increasingly complex and rich in opportunities for usability heuristics to be explored and applied. Since the elements of VR, AR, and MR are integrated into the metaverse, it is necessary to re-evaluate traditional usability principles to correspond with its idiosyncrasies.

This study identifies significant usability challenges in the metaverse, such as information overload, navigational complexity, and intuitive control mechanisms. The immersive nature of this realm further complicates these problems, since it requires the seamless integration of physical and digital worlds for good UXs. This investigation stresses different specific usability heuristics adapted for the metaverse due to its distinct interaction paradigms and user expectations.

The third section of the article proposes a comprehensive methodology for developing usability heuristics tailored specifically for metaverse UIs. This approach is critical in addressing the identified unique challenges posed by the metaverse, which includes 3D interactions, immersive experiences, and social dynamics. Several relevant studies and heuristic models provide a foundation for this research, including those by Jakob Nielsen, Sutcliffe and Gault, Endsley and others, and Rusu and others. Therefore, this research strives to synthesize existing usability models by adapting them for use in the metaverse. In summary, this paper proposes an extensive list of 52 heuristics, which have been enriched with 156 sub-heuristics that cater to 3D interactions, immersive experiences, and social dynamics within VEs. These heuristics aim to enhance user engagement, ensure accessibility, and maintain user satisfaction across diverse demographic groups. Furthermore, the proposed heuristics and sub-heuristics can be considered as a foundation upon which designers and developers can create user-friendly, engaging, and inclusive metaverse environments.

Additionally, this research indicates that these heuristics and sub-heuristics should be continually adapted and refined as the metaverse changes. They also encompass ethical issues, privacy concerns, and the integration of economic transactions and inclusiveness.

Finally, it is important to note that this research contributes significantly to the understanding of usability in the metaverse by proposing bespoke heuristics that cater for its unique difficulties and benefits. These heuristics will be vital in maintaining intuitive, immersive, and enjoyable UXs as the metaverse continues to absorb itself into different aspects of everyday life. Furthermore, this research proposes a structured and methodical approach that consists of seven steps to assess the adequacy of the 52 heuristics and 156 sub-heuristics identified. However, the dynamic nature of technology, the need for empirical validation, and the balance between generalization and specificity are important considerations that must be addressed to ensure the ongoing relevance and effectiveness of these guidelines.