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Citation: Traub, M.; Weinberger, M.
APIs in the Metaverse—A Systematic
Evaluation. Virtual Worlds 2024,3,
157–170. https://doi.org/10.3390/
virtualworlds3020008
Academic Editor: Christos J. Bouras
Received: 11 December 2023
Revised: 31 January 2024
Accepted: 3 April 2024
Published: 8 April 2024
Copyright: © 2024 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Article
APIs in the Metaverse—A Systematic Evaluation
Marius Traub and Markus Weinberger *
Faculty of Electronics and Computer Science, Aalen University of Applied Science, 73430 Aalen, Germany;
mariustraub@outlook.de
*Correspondence: markus.weinberger@hs-aalen.de
Abstract: One of the most critical challenges for the success of the Metaverse is interoperability
amongst its virtual platforms and worlds. In this context, application programming interfaces (APIs)
are essential. This study analyzes a sample of 15 Metaverse platforms. In the first step, the availability
of publicly accessible APIs was examined. For those platforms offering an API, i.e., Decentraland,
Second Life, Voxels, Roblox, Axie Infinity, Upland, and VRChat, the available API contents were
collected, analyzed, and presented in the paper. The results show that only a few Metaverse platforms
offer APIs at all. In addition, the available APIs are very diverse and heterogeneous. Information is
somewhat fragmented, requiring access to several APIs to compile a comprehensive data set. Thus,
standardized APIs will enable better interoperability and foster a more seamless and immersive user
experience in the Metaverse.
Keywords: Metaverse; application programming interface (API); interoperability; standards
1. Introduction
The Metaverse represents an epicenter of innovation, where a confluence of events, cor-
porate activities, virtual real estate, and user-generated experiences creates an increasingly
vibrant digital ecosystem [
1
]. Many researchers define the Metaverse as an interconnected
web of virtual worlds in which users represented by avatars connect and interact with
each other [
2
]. The attraction of the Metaverse lies not just in its potential for human
interaction but also in the economic opportunities it presents—a digital universe filled
with potential yet to be fully discovered. The Metaverse can have a many applications in
many domains, ranging from industry, where production plants can be virtually simulated
before construction [
3
], to education, where remote participants can learn and practice even
manual tasks [4].
As the Metaverse is envisioned to comprise a plurality of virtual worlds, interop-
erability between these virtual worlds is an essential success factor [
5
]. Interoperability
in the Metaverse ensures that assets, identities, and information can move freely across
various environments, which is essential for creating a unified virtual experience. This
fluidity is critical for user engagement and the long-term viability and evolution of the
Metaverse [
6
,
7
]. Interoperability can have various aspects, e.g., transferability of assets
or digital currencies between virtual worlds, which is related to file formats amongst
other topics [
8
]. For example, the service Ready Player Me, which allows the creation of
cross-platform avatars that can easily be transferred between virtual worlds, addresses
this aspect of interoperability [
9
]. The article focuses on data and information exchange
between virtual worlds and other information systems. Making data from a virtual world
accessible from the outside is an essential precondition for services providing an overview
of the Metaverse and its offerings. Such services could be catalogs or search engines listing
events, experiences, addresses of shops, and the like in virtual worlds.
In the Internet, specifically the World Wide Web, as we know it today, Application
Programming Interfaces (APIs) play an important role, enabling data exchange between
web services [
10
]. Similarly, APIs could connect virtual worlds to each other and any web
Virtual Worlds 2024,3, 157–170. https://doi.org/10.3390/virtualworlds3020008 https://www.mdpi.com/journal/virtualworlds
Virtual Worlds 2024,3158
service. For example, APIs could be the technical basis for building catalogs and search
engines listing information across virtual worlds, such as events, land ownership, and
experiences. Thus, APIs have the potential to serve as gateways, offering structured and
user-friendly access to diverse and rich information within the Metaverse. Using APIs, the
Metaverse’s layers could be decoded and made available to a broader audience, facilitating
a deeper engagement with this virtual space.
In light of these considerations, this paper articulates the following research questions:
R1.
What APIs are currently available in the Metaverse?
R2.
What information can be retrieved through the available APIs?
This investigation aims at making the following contributions to the Metaverse community:
•The study gives an overview of which virtual worlds from a sample offer APIs.
•
The paper provides a guide to information accessible through APIs provided by
virtual worlds.
•
The study compares APIs regarding the available information and identifies generic
weaknesses and future research directions.
The structure of this article is organized to provide a comprehensive understanding of
the current state of APIs in the Metaverse. Section 1presents related work to prove that this
article addresses a relevant research gap and an introduction to API technology. Section 2
outlines the applied methodology, detailing the approach used to select and systematically
examine various Metaverse platforms and the criteria for API evaluation. Section 3presents
the findings and provides a detailed overview of the available APIs in these environments.
Section 4finally discusses the diversity and complexity of Metaverse APIs, examining the
challenges and potential opportunities for future research and development.
1.1. Related Work
A structured search was conducted to collect the relevant literature and existing
research related to Metaverse APIs. This search aimed to identify existing comparisons,
surveys, and studies focusing on APIs within the Metaverse.
The databases Google Scholar, Web of Science, and Scopus were each searched for
the following terms: “Metaverse API comparison”, “Metaverse API interoperability”,
“Metaverse API survey”, “Virtual World API comparison”, and “Virtual World API inter-
operability”. The first ten results for each search term on each platform were analyzed,
ensuring a balance between the comprehensiveness and manageability of the literature
review. After removing duplicates, this approach led to an initial pool of 83 unique results.
Upon a closer examination of these results, we found that only three of these studies
were relevant to our research focus, specifically addressing APIs in the context of the
Metaverse. These studies were then selected for a more detailed review and comparison.
For their article “Blockchain-based Asset Storage in the Metaverse (MetaRepo)”, Ersoy
and Gürfidan developed a blockchain-based solution for secure digital asset storage and
transactions in the Metaverse. The paper diverges from the API-centric approach of
this article by focusing on blockchain infrastructure. However, it aligns with this paper
through its use of APIs for enhancing Metaverse interoperability and security [
10
]. The
article “Privacy Risks in Metaverse Applications (METAseen)” by Yu et al. concentrates on
platforms like Decentraland and Sandbox. This research systematically analyzes privacy
policies and network traffic, revealing critical data privacy concerns in the Metaverse.
The findings highlight the need for privacy-conscious and secure API development [
11
].
Fang and Cai finally address the topic of interoperability in 3D virtual worlds. They
propose using RESTful Web Services to facilitate communication across various platforms.
The paper underscores the importance of interoperable and scalable APIs, resonating
with this paper’s objective of creating an overview of existing API solutions for virtual
world platforms.
While ample research on various aspects of the Metaverse is available, including its
conceptual framework, technological infrastructure, and social implications, the specific
Virtual Worlds 2024,3159
exploration of APIs still needs to be addressed. No scientific survey could be identified
comprehensively depicting APIs available in today’s virtual worlds. Thus, the need for
more specific studies focusing on existing APIs within the Metaverse is a gap in current
academic research. This observation sets the stage for the importance and novelty of the
study at hand, which aims to fill this gap by systematically evaluating APIs across various
Metaverse platforms. This approach offers a new perspective on how APIs contribute to
the functionality and expansion of virtual environments.
1.2. API Technology
Application Programming Interfaces (APIs) are the links between different software
components [
12
]. They allow for the integration of diverse systems and are instrumental in
achieving interoperability within the Metaverse [
6
,
13
]. APIs define the methods and data
formats that applications use to communicate with each other and users, serving as the
building blocks for complex digital ecosystems [
12
]. The following types of APIs can be
distinguished:
•
RESTful APIs: Representational State Transfer (REST) APIs are widely used for web ser-
vices and are known for their scalability and simplicity. They use standard HTTP meth-
ods and are stateless, making them ideal for public services in the Metaverse [14,15].
•
GraphQL APIs: GraphQL is a query language for APIs that provides a more efficient
and powerful way to work with data [
16
]. It allows clients to request exactly what
they need, making it useful for Metaverse applications where data requirements are
complex and varied [16].
•
SOAP APIs: Simple Object Access Protocol (SOAP) APIs are protocol-based and
known for their standardized format and extensive feature set, including built-in error
handling and security [17].
In addition, the following technical differences were considered when analyzing APIs:
•
Communication Patterns: RESTful APIs operate on a request-response model, SOAP
APIs use a service-oriented approach, and GraphQL allows for dynamic queries and
mutations [18].
•
Data Format and Structure: REST typically uses JSON or XML for data exchange [
15
];
SOAP uses XML for messaging [
17
]; GraphQL employs a flexible query structure [
19
].
•
Performance: REST APIs are stateless, SOAP can maintain state with WS-* standards,
and GraphQL optimizes performance by fetching only required data [15,20,21].
•
Error Handling and Security: SOAP has robust error handling and built-in security
standards like WS-Security [
21
]. RESTful APIs handle errors through HTTP status
codes and GraphQL through query validation [22].
Each type of API brings its unique advantages. Understanding these differences
is crucial for designing systems that are not only interoperable but also efficient and
user-friendly.
2. Methodology
This study utilized a systematic methodology to examine the application programming
interfaces (APIs) across selected Metaverse platforms, focusing on their interoperability,
which is crucial for the Metaverse’s functionality.
2.1. Sample Selection
Popular virtual worlds were chosen for this study that implement critical features of
the Metaverse. The following key features were identified from widely accepted Metaverse
definitions [2].
•
Persistence: The platform’s ability to offer continuous, uninterrupted virtual experi-
ences is essential. Persistence ensures that the digital environment and user-generated
content remain accessible over time.
Virtual Worlds 2024,3160
•
Immersiveness: An essential attribute of the Metaverse, immersiveness refers to how
convincingly the platform can engage users in a virtual environment. It includes
sensory engagement and the depth of interaction within the virtual world.
•
Social Interaction: The extent to which the platform supports and facilitates user
interaction and social connectivity. This criterion evaluates how the platforms enable
community building, collaboration, and social experiences.
•
Accessibility: Accessibility is critical for broad adoption and usability. It encompasses
the ease of access to the platform, user-friendliness, and the inclusivity of different
user groups.
•
Decentralization: Given the evolving nature of the Metaverse, decentralization is a
forward-looking criterion. It reflects the platform’s approach to governance, data
control, and power distribution among users and developers.
As the Metaverse is still in its infancy, no virtual worlds exist that implement all the
essential features listed above to a full extent [
23
]. On the other hand, these criteria help
distinguish Metaverse platforms from 3D games like Fortnite or Minecraft, which reset
the game world after each round [
24
] or only allow for minimal social interaction [
25
].
While not every platform in the sample embodies all the critical aspects of persistence,
immersiveness, social interaction, accessibility, and decentralization to the same degree,
each platform selected for the study demonstrates most of these criteria. These platforms
serve as the primary subjects of our systematic evaluation, providing a comprehensive
overview of the current landscape of APIs in the Metaverse. They are listed in Table 1.
Table 1. Sample of Metaverse platforms and API availability.
Metaverse Platform Accessible Public API Available
Axie Infinity Yes
Captic No
Decentraland Yes
EngageVR No
Horizon Worlds No
MONA No
Roblox Yes
Sansar No
Second Life Yes
Somnium Space No
Spatial No
The Sandbox No
Upland Yes
Voxels Yes
VRChat Yes
In the next step in the research process, the availability of APIs for the sample platforms
was examined. This investigation focused on whether the platforms offered interfaces for
programming and integrating external applications. This analysis revealed a narrowed list
of seven platforms for which relevant APIs were available.
2.2. API Research Methodology
A multi-level approach was used to collect data regarding the available APIs of the
chosen Metaverse platforms:
Virtual Worlds 2024,3161
•
Website Analysis: The official websites and developer documentation of the Metaverse
platforms were examined. This analysis focused on identifying publicly available
APIs, their features, and the scope of access they provided.
•
Community Engagement: Active engagement with the developer community was con-
ducted mainly through Discord channels. These discussions offered insights into the
practical uses of the APIs and additional information not available in official documentation.
•
Direct Correspondence: Where necessary, direct communication with the develop-
ment teams of the Metaverse platforms was established via email. This method was
employed to clarify details, gain further information, and request access to APIs where
public information was insufficient.
The APIs and interfaces were cataloged based on their public accessibility and tailored
functionalities for content creators within the Metaverse. The resulting data were tabulated
to provide a clear overview of the Public APIs available for each Metaverse platform and
their accessibilities as of the research time.
3. Results
The research process for this study involved several steps, as explained in Section 2.
The following Sections present the results of the respective steps.
3.1. Identification and Evaluation Process
In the first step of our study, Metaverse platforms were collected, including a check
on whether the candidate platforms meet the Metaverse criteria, explained in Section 2.1.
This first step resulted in a sample of 15 Metaverse platforms, depicted in Table 1. The
second step involved a meticulous examination to determine whether each platform had
an API, focusing on public APIs’ availability and accessibility. This process was critical to
understanding how these platforms could be integrated into broader systems or accessed
for data extraction and interaction.
The evaluation process involved the following stages:
•API Existence Check: Determining if the Metaverse platform offers any API.
•
Public API Assessment: Identifying whether the APIs are public, ensuring external
users and developers can access them.
•
Accessibility Verification: Confirm these APIs’ ease of access and usage, including the
availability of documentation and developer support.
Platforms that lacked accessible public APIs were systematically excluded from the
sample. This filtering ensured that our final selection represented Metaverse platforms
with available and practically usable APIs for external purposes. The result of step 2 is
included in Table 1, too.
The Metaverse platforms selected for further examination encompass a range of virtual
environments, each with distinctive characteristics and user base. The refined sample for
our API research comprises platforms that met our criteria for having accessible public APIs:
•
Axie Infinity: A digital pet universe where players breed, raise, battle, and trade
fantasy creatures called Axies [26].
•
Decentraland: An open-world virtual reality platform that leverages the Ethereum
blockchain to provide a decentralized user-owned environment [27].
•
Roblox: A platform that revolutionized user-generated content, providing a suite of
tools for users to create their own experiences [28].
•
Second Life: One of the earliest and most mature virtual worlds, offering rich user
interactions and a complex economy [29].
•
Upland: A virtual property trading platform mapped to the real world, allowing users
to buy, sell, and trade virtual properties [30].
•
Voxels: Focused on simplicity and ease of use. This platform allows users to create
and trade virtual assets on the blockchain [31].
Virtual Worlds 2024,3162
•
VRChat: A social virtual reality platform that enables users to interact with others in
various immersive, user-created worlds [32].
3.2. Available APIs
This Section presents various aspects of the available APIs. Section 3.2.1 presents
a comprehensive overview of all available APIs for the six virtual worlds presented in
Section 3.2. Section 3.2.2 provides more detail on selected API endpoints to further illustrate
the heterogeneity of Metaverse APIs. Finally, Section 3.2.3 compares the information made
available through the provided APIs.
3.2.1. Comprehensive Overview of Available APIs
This Section presents detailed information about the available APIs. This illustrates
the range of functionalities and critical features these APIs offer, providing insights into the
diverse capabilities and limitations inherent in each platform’s approach to virtual world
interaction and data accessibility. The table serves as a reference point in understanding
the current state of API offerings within the Metaverse landscape.
Table 2presents a comprehensive overview of the APIs identified for the Metaverse
platform Decentraland.
Table 2. Overview of Decentraland APIs.
APIs Identified Description and Key Features
Tiles API [33]
The endpoint returns all tiles in the Decentraland map.
This API is key for accessing detailed data about the
virtual land parcels in Decentraland. In Decentraland, a
tile represents the smallest unit of land, similar to a
single square on a chessboard. These tiles are
collectively known as parcels, the basic building blocks
of the Decentraland world.
Parcel API [33]
The endpoint returns metadata about a specific parcel by
its coordinates using the OpenSea Metadata Standard
[
34
]. A parcel in Decentraland is a single tile or a unit of
land that players can own and develop. Parcels are 3D
spaces where users can create experiences, games, or
other interactive content.
Estates API [33]
The endpoint provides metadata about an estate that
comprises several contiguous parcels (or tiles) by its ID.
An estate is a larger piece of land made by grouping
adjacent parcels. Estates allow for the creation of more
extensive developments.
Districts API [33]
The endpoints return information about all districts or
specified districts in Genesis City. Districts in
Decentraland are large areas comprising multiple
parcels, usually centered around a specific theme or
community. They are akin to neighborhoods or sectors
within a city, providing a communal space for users with
similar interests.
Map API [33]
The endpoint returns a PNG of the genesis map,
customizable via various query parameters such as
width, height, and center coordinates. It provides a
bird’s-eye view of Decentraland, showcasing the layout
of parcels, estates, and districts.
Event API [35]
The endpoint provides information about upcoming
events. It includes details like event names, descriptions,
dates, and coordinates, facilitating the discovery and
participation in various virtual events.
Virtual Worlds 2024,3163
Table 3presents APIs available in Second Life.
Table 3. Overview of Second Life APIs.
APIs Identified Description and Key Features
Registration API [36]
This API allows for registering Second Life residents
directly from a web page. It streamlines adding new
users to the Second Life community by integrating the
registration process into external websites.
Map API [36]
This API allows for embedding Second Life maps onto
web pages. This is particularly useful for integrating
Second Life features into external platforms or creating
custom user interfaces.
Live Data API [36]
Linden Lab provides live data feeds that offer real-time
information relevant to the Second Life environment,
such as current events or user activities.
Inventory API [36]
This API provides information on agent inventory
within Second Life. It is crucial for managing and
accessing the inventory data of users.
Search API (unofficial) [37]
This API enables searching within Second Life for
events, groups, people, and places and also facilitates
searching the Second Life Wiki.
Voxels offers the APIs depicted in Table 4.
Table 4. Overview of Voxels APIs.
APIs Identified Description and Key Features
Parcels API [38]Returns details about every parcel in Voxels, including
the owner, collaborators, description, and geometry.
Single Parcel API [38]
Provides basic information for a specific parcel in Voxels
when given the parcel’s ID as a parameter. This API
focuses on individual parcel data.
AllFeaturesParcel API [38]
Returns all features inside a specific parcel based on the
provided parcel ID and goes deeper into the details of a
specific parcel, revealing all its features (e.g., items or
structures) when provided with the parcel’s ID.
Suburbs API [38]The endpoint offers information about all suburbs in
Voxels, including their characteristics and locations.
Islands API [38]
Provides a list of all islands in Voxels and their
geometric data, giving a comprehensive overview of
these distinct areas within the virtual environment.
Womps API [38]
Returns the last 100 womps (user-generated messages or
actions) and their associated information in Voxels.
Avatars API [38]
The endpoint gives information about avatars, including
details of their corresponding parcels. This API links
virtual characters to specific locations in Voxels.
Collectibles API [38]
The endpoint provides information on all collectibles
within Voxels, including details about each collectible
item.
The Roblox APIs are presented in Table 5.
Virtual Worlds 2024,3164
Table 5. Overview of Roblox APIs.
APIs Identified Description and Key Features
Users API [39]
This API handles direct Roblox user information. It
provides access to user-related data, such as profiles,
statistics, and other critical user-specific details.
Avatar API [39]
This API focuses on the customization of player avatars.
It includes endpoints for modifying and retrieving
information about player avatars.
Catalog API [39]
Enables browsing and searching for catalog items. It also
recommends content and user-based catalog items.
Games API [39]
This API provides valuable data for game discovery. It
includes endpoints for retrieving detailed information
about games available on Roblox.
Groups API [39]
Manages groups within Roblox, including creating,
managing, and moderating user groups. This API is
essential for community building and management on
the platform.
Presence API [39]
It contains all endpoints for managing user presence. It
helps track and display the online status and activity of
users.
Inventory API [39]
It focuses on viewing (but not granting) ownership of
items. Users must manage and view their in-game
inventory, including items owned, collected, or earned
through gameplay.
Premium Features API [39]
This API plays a crucial role in managing premium
subscriptions and features available to users who opt for
the premium service on Roblox.
Table 6presents APIs available in Axie Infinity.
Table 6. Overview of Axie Infinity APIs.
APIs Identified Description and Key Features
Item API [40]
This API includes endpoints for listing all
runes, charms, and other items and retrieving
specific items by ID. It is used for managing the
different items available in the game.
User Item API [40]
With the query parameter of the UserID, all
Items of the given user are displayed in the
format of the Item API.
User Map API [40]
With the query parameter of the UserID, all the
cleared Chapters of the given user are
displayed.
User Fighter API [40]
With the query parameter of the UserID, all the
fighters of the given user are displayed.
Leaderboard API [40]
This API Lists the current leaderboard of
players and the current season leaderboard.
The maximum number of players in the
response object can be limited with
query parameters.
Season API [40]This API shows basic information about the
current Season.
An overview of APIs for Upland is depicted in Table 7.
Virtual Worlds 2024,3165
Table 7. Overview of Upland APIs.
APIs Identified Description and Key Features
Tracks API [41]
This API response provides an overview of a track in
Upland, offering details like location, physical attributes,
and conditions that can be used for game mechanics or
player decision-making.
Tracks Buildings API [41]This API response describes a building in Upland,
including its physical characteristics and location.
Cities API [41]
This API response provides information about cities in
Upland, listing each city with a unique identifier and its
name.
Properties API [41]
This API lists information about properties in Upland,
detailing their location, status, and related financial
information.
Table 8presents information on VRChat APIs.
Table 8. Overview of VRChat APIs.
APIs Identified Description and Key Features
Avatars API [42]
This endpoint manages avatar data within VRChat. It
provides details such as the avatar’s unique ID, author
information, creation and update timestamps, and
description. The API also includes the avatar’s image URLs,
release status, tags, and unity package details, which are
crucial for avatar customization and management.
Groups API [42]
This endpoint handles group-related data in VRChat. It
includes the group’s ID, name, short code, and other
descriptive information. The API also manages group icons,
banners, owner details, member count, and tags, offering
insights into group characteristics and dynamics.
Additionally, it covers galleries within groups,
encompassing details like ID, name, description, and roles
for viewing and submitting content.
Users API [42]
This endpoint provides comprehensive user profile
information in VRChat. It includes bio, current avatar
images, display name, user ID, friendship status, and
platform information. The API also covers status
descriptions, tags, user icons, and location, which are
essential for user profile management and social interaction
within VRChat.
Worlds API [42]
Provides detailed information about the virtual worlds or
experiences within VRChat. Key data includes the world’s
unique identifier, author information, capacity,
recommended capacity, creation and update timestamps,
and encompasses retrieving world metadata and exploring
world categories.
Economy API [42]
This Endpoint is essential for managing VRChat’s virtual
economy and user subscriptions and manages transactions
and subscriptions within VRChat. It details transaction ID,
status, subscription information (including ID, steam item
ID, amount, description, period, and tier), sandbox status,
creation/update timestamps, and
steam-related information.
Virtual Worlds 2024,3166
3.2.2. Details on Selected API Endpoints
As can be seen from Tables 2–8, each Metaverse platform offers individual APIs
that differ in name, content, and specification from other platforms’ APIs. The following
selected examples are explained in more detail to illustrate the variety of functionalities of
these APIs:
•
Decentraland’s Tiles API: The Tiles API in Decentraland has been updated to a more
efficient v2 endpoint. It returns detailed information about all tiles in the map in a new,
more readable format. This API is crucial for accessing comprehensive data about
virtual land parcels in Decentraland, offering insights into the layout and distribution
of land.
•
Decentraland’s Estates API: The Estates API in Decentraland allows users to retrieve
metadata about an estate based on its ID. An estate represents a building or facility of-
ten stretching across multiple tiles. This functionality is essential for accessing detailed
information about estate properties, including their ownership and characteristics.
•
Voxels Parcel API: The response provides detailed information about a parcel in the
virtual world. An example response includes data such as the parcel’s ID, dimensions,
location coordinates, contributors, and ownership details. However, a blockchain
explorer like Etherscan [
30
] is essential for comprehensive insights, especially on
transaction history and ownership changes. It complements the API by providing
deeper transactional data, which is crucial for understanding the full economic context
of each parcel.
•
Roblox’s Avatar API: In Roblox, each user is represented by a customizable avatar.
The Avatar API provides functionalities for character model customization, allowing
users to interact with experiences and personalize their avatars with a wide range of
clothing and accessories available in the Roblox Marketplace. This API is a cornerstone
for user identity and personalization within the Roblox platform.
•
Second Life’s Map API: The Map API of Second Life enables the integration of dynamic
Second Life maps into websites or applications. It provides a way to embed real-time
maps showing the virtual world’s layout, including regions and significant landmarks.
Developers can use this API to create interactive map features for users, enhancing
navigation and spatial awareness in the Second Life Metaverse.
3.2.3. Comparison of Available APIs
The virtual worlds providing APIs cover a variety of information made accessible
through respective endpoints. Table 9presents an overview of the available information
per virtual world. As can be seen, none of them covers the full range of information. Roblox
comprises many closed experiences instead of an open, explorable landscape [
28
]. This
renders information on a virtual property, district, or map meaningless. In light of this
consideration, the Roblox API provides the most comprehensive information in the sample.
On the other hand, Upland focuses primarily on trading virtual property [
41
], making
corresponding APIs reasonable. In this case, an additional map API, which is not available
today, could also be beneficial. Information on events and experiences could be specifically
helpful to gain users’ attention and drive traffic to a virtual world. Nevertheless, only
Decentraland, Roblox, and VRChat offer corresponding APIs. Live data could enable users
to determine whether and where friends are active in a virtual world. The majority offers
respective APIs, but not all of the worlds in the sample.
Virtual Worlds 2024,3167
Table 9. Overview of available information.
Available Information
Decentraland
Second Life
Voxels
Roblox
Axie Infinity
Upland
VRChat
Virtual Property Information
(e.g., ownership or characteristics of land, parcels, estates) X X X
District, Island, or Neighborhood Information
(e.g., community topics) X X X
Map X X X
Event and Experience Information
(e.g., topics, types, dates, location) XXX
Admin Functions
(e.g., register users, user groups, season data) X X X X
Live Data
(e.g., user activity, leader board, presence, messaging, economy) XXXX X
User and Avatar Data
(e.g., public account data, inventory) XXXX X
Asset and Collectible Information
(e.g., properties, IDs) XXX
4. Discussion
Table 1shows that only 7 platforms of a sample with 15 platforms offer publicly
accessible APIs. Thus, most sample platforms do not provide this widespread and widely
accepted means of interaction and interoperability.
A distinct diversity and complexity become apparent when examining the available
APIs of various Metaverse platforms. While allowing for unique and tailored experiences
in each virtual world, this variety also creates a barrier to the interoperability of different
Metaverse environments. In particular, significant marketplaces such as OpenSea [
43
]
could be pivotal in driving standardization across various APIs, particularly in domains
like real estate and other digital assets. Their widespread usage and influence in the digital
asset market could set a precedent for uniform API structures and data formats, thereby
supporting a more cohesive and efficient approach to data management in the Metaverse.
An additional critical issue is the fragmentation of information accessible through
these APIs. For many virtual worlds, generating a comprehensive picture requires accessing
several APIs, including sources outside the respective virtual platform. This underscores
the need for a more unified approach to data management and retrieval within the Meta-
verse. The varying levels of complexity and data availability across platforms necessitate
customized strategies, leading to inefficiencies in both development and user experience.
While internal APIs like the Voxels Parcel API provide foundational data, they often need
more detailed historical and transactional context. The reliance on external sources reflects
a broader need within the Metaverse for APIs to provide a more comprehensive data
spectrum. Blockchain explorers are essential tools that provide historical and economic
data on virtual assets, which are crucial for the analysis and traceability of Metaverse’s
digital assets. This underscores the potential for evolving API offerings to deliver more
integrated data solutions within these virtual environments.
For users, the current limitations of APIs may restrict the scope of interaction and im-
mersion in virtual worlds. For developers, it represents a challenge in navigating a diverse
and sometimes limited API landscape. Addressing these issues could significantly enhance
the user experience and the ease of development within the Metaverse. This scenario
presents an opportunity to develop more standardized and comprehensive APIs within the
Virtual Worlds 2024,3168
Metaverse. Such advancements could improve interoperability between different virtual
environments and provide a more seamless experience for both users and developers.
The study examined a sample of 15 virtual world platforms. As the number of available
Metaverse platforms is at least in the hundreds [
44
], this poses a significant limitation. In
addition, the Metaverse is developing rapidly. Thus, the API landscape might change, too.
Future research could examine larger and updated samples and re-evaluate the results of
this study.
Furthermore, following a user-centered approach, future research could evaluate
which API topics are specifically interesting from a user point of view. In this respect,
users could be Metaverse users, visitors of virtual worlds, content creators, and developers
alike. A proposal for standardized APIs addressing user needs should be developed in the
second step.
5. Conclusions
The Metaverse is envisioned as a network of interconnected virtual worlds [
2
,
8
],
emphasizing the need for interoperability. While this includes, but is not limited to, aspects
such as standardized data formats for 3D objects, avatars, and in-world experiences, the
paper at hand focuses on interfaces for the data exchange between virtual worlds or
with other web services. This study revealed that only a fraction of the examined virtual
world platforms offer APIs at all. The available APIs have been analyzed regarding their
functionality and the accessible information. Thus, this study contributes a guide to today’s
Metaverse APIs.
Furthermore, this study revealed that in most cases, the accessible information is
limited, and gathering meaningful information, in many cases, requires complex queries,
and the APIs are very different for specific virtual worlds. This is an essential barrier
for interoperability in the Metaverse and, thus, for the Metaverse itself. Future research,
industry, and developers should focus on standardizing API and data structures to foster
Metaverse adoption and success. An excellent example of the power of standardization is
the ERC20 standard [
45
] in the Ethereum ecosystem. ERC20 defines a standard interface
for smart contracts on the Ethereum blockchain defining tokens. ERC20 was introduced in
2015 [46]. Today, it accounts for 80% of initial coin offerings [47].
Author Contributions: Conceptualization, M.W.; methodology, M.T. and M.W.; investigation,
M.T.; data curation, M.T.; validation, M.W.; writing—original draft preparation, M.T. and M.W.;
writing—review
and editing, M.W. and M.T.; supervision, M.W. All authors have read and agreed to
the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: The original contributions presented in the study are included in the
article, further inquiries can be directed to the corresponding author.
Conflicts of Interest: The authors declare no conflicts of interest.
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