User-Generated Content and Editors inVideo Games: Survey and Vision
Haihan Duan, Yiwei Huang, Yifan Zhao, Zhen Huang, Wei Cai*
School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, China{haihanduan, yiweihuang, yifanzhao, zhenhuang1}@link.cuhk.edu.cn, caiwei@cuhk.edu.cn

Abstract—User-generated content (UGC) is any form of content that has been created by users rather than the developers of
online platforms. The UGC has been playing a very importantrole in video games. For instance, Counter-Strike (CS) and
Defense of the Ancients (DOTA) originated from modificationsof Half-Life and Warcraft III: Reign of Chaos respectively. As
a promising trend, the UGC will be increasingly developedand extended to wider scopes in virtual worlds, such as themetaverse, which is highly promising for further study in bothacademia and industry. However, there are few existing surveys
that systematically discuss the UGC in video games. In this paper,
we systematically review the representative UGC in video games
and their corresponding UGC editors based on a decision treestyle classification method. Then we enumerate the propagation
methods of UGC in video games. Moreover, we propose our visionof the future development of UGC in the metaverse.
Index Terms—User-Generated Content, Video Game, Game
Editor, Metaverse.

I. I NTRODUCTION
The user-generated content (UGC) is any form of content
that has been created by users rather than the developers of
online platforms [1]. On the Internet, the classic UGC includes
text, audio, video, animated material, etc [2], and these UGC
represent the creativity, innovation, and delivery ability ofusers, which has shown an amazing power in promoting thedevelopment of online media communities [3].
Similarly, the evolution of video games is also benefit a
lot from UGC [4]. The most famous cases are CounterStrike (CS)1 and Defense of the Ancients (DOTA)2 . Thereinto,
CS originated from a modification (MOD) of Half-Life3 , a
first-person shooting (FPS) video game, while DOTA is amultiplayer online battle arena (MOBA) MOD of Warcraft
III: Reign of Chaos4 . The two representative games deeply improve the players’ perspective, understanding, and acceptanceof UGC in video games. Besides, the UGC in video games hasvarious forms, including but not limited to game levels, userinterface (UI), game character graphic alterations (so-calledskins), etc [5], which significantly improves players’ gaming
experience. With the growing trend of UGC and their culture,community, and economics, the UGC gives the creators andplayers a sense of participatory involvement and also increases
their enjoyment with digital games [6], [7].
*Wei Cai is the corresponding author (caiwei@cuhk.edu.cn).
1 https://blog.counter-strike.net/
2 https://www.dota2.com/home
3 https://www.half-life.com/
4 https://playwarcraft3.com/

There have been some related studies that review the development or impact of general UGC [2], [8]–[10]. Moreover,existing studies also conducted surveys on specific areas, including online brand communities [11], brands marketing [12],tourism [13], hotel experiences [14], digital well-being [15],social media [16], etc. However, there is only a small numberof studies focusing on the UGC and their corresponding editors
in digital games [4], [17], [18], while few of them illustrated
detailed taxonomy or classification of the UGC in video
games. Therefore, this paper intends to systematically survey
the existing UGC and their corresponding content editors ofsome representative and notable video games, and provide ourvision about the future development of UGC in the area ofgamification, especially in the metaverse.
The remainder of this paper is organized as follows. We
briefly review some previous works about UGC in video gamesin Section II. Then, we discuss and classify the UGC in video
games in Section III and their corresponding UGC editors
in Section IV. Afterward, we enumerate some representative
propagation methods of video game UGC in Section V. And
we propose our vision for the future development of UGC invideo games in Section VI. Section VII concludes the paper.
II. R ELATED W ORK
In recent years, the UGC in video games gradually prospered and had a unique and significant impact on the gaming
field, which also attracted the attention of the academic
community. For example, early in 2007, Lastowka et al. [17]studied the relationship between the UGC and general virtualworlds, in which the paper mainly discussed the practicaland legal problems of the creation of UGC in virtual worlds.
Kasapakis et al. [6] studied the UGC in a pervasive roleplaying game for investigating the effect of UGC under
diverse technical, functional, and gameplay characteristics. In
2015, Linberg et al. [4] conducted a quantitative study on
members of 4 online video game UGC communities, and thendeeply examined the effects of motivational factors of intrinsic
motivation, extrinsic motivation, and toolkits that motivate
game players to participate in UGC creation. Sotamaa et al.
[5] mainly explained the concept, history, and types of gameMODs, and also discussed the motivations of the creators andreactions of the game industry. However, the existing surveys
did not illustrate a systematic review of the UGC and its
creation tools, while they mainly focused on the social effects

of UGC in video games, such as the motivational factors of
UGC creation, the perspective of the game industry, etc.
Correspondingly, the development toolkits or editors arenecessary for creating the UGC and directly affect the user’s
creation experience. Currently, there are also some researchers
who have studied how game editors influence game UGC creation using different technologies. Liapis et al. [19] introduced
Sentient Sketchbook, a tool that supports a designer in thecreation of game levels, which used map sketches to alleviate
designers’ efforts. Ng et al. [20] focused on the augmented
reality (AR) environment and explored the concept and designof level editors in AR games. For studying the co-creation invideo games, Davidovici-Nora [21] pointed out a new hybrid
innovation model used to develop World of Warcraft (WoW), a
massively multiplayer online role-playing game (MMORPG).
Besides, there are also many studies that applied artificial
intelligence (AI) methods to support UGC creation in video
games. For example, Summerville et al. [22] examined theuse of Long Short-Term Memory (LSTM) recurrent neuralnetworks for generating levels for Super Mario Bros. Guzdial
et al. [23] presented an unsupervised process to generate fullvideo game levels trained on gameplay video of Super Mario
Bros. Moreover, a detailed discussion about how the design ofan AI-driven game level editor affects creators was conductedby Guzdial et al. [24]. However, the published works mainly
proposed novel methodologies or practical designs for thedevelopment toolkits and editors, while few of them systematically survey the existing game editors.
III. C ATEGORIES OF U SER -G ENERATED C ONTENT
In video games, the imagination, innovation, and creative
ability of players are unlimited, in which there are various
UGC created with countless forms and styles, which makes
the classification of the UGC using the traditional taxonomy
methods difficult. Therefore, in this paper, we construct a
decision tree-style classification Venn diagram according to
the impact of the UGC on the basic video games, as shownin Fig. 1, and we also list some representative games foreach type. Besides, Fig. 1 also contains the classification
map of UGC editors, which will be studied in Sec. IV.
Note that, one representative game will only be selected once
although they might have multiple kinds of UGC and editors.
In the following subsections, we will discuss the definition,
characteristics, and representative games of each type in detail.
A. User-generated Game Modes
Currently, most games provide the default rules, maps,
characters, and targets so that the players can follow theguidance to finish the whole story of the game. However, using
the game as a framework, users can generate new game modes
by modifying the original rules of the base games, which areuser-generated game modes.
For the user-generated game modes, the representative pointis that this kind of UGC provides new ways for gameplay. Or,
the goal of the base games is to build a platform for users tocreate new modes. In this paper, the definition of game modes

is not limited as discussed by Heintz et al. [25], while it has amore general scope for even tiny modifications. For example,
in FPS games, if the user-generated game mode provides
a shorter time to kill (TTK), it can be regarded as a new
game mode. In fact, the shorter TTK mode already exists inmany FPS games (e.g. CrossFire5 ). Therefore, we consider thatthe new game modes do not have to be completely different
from the base games, but they should provide novel gaming
experiences that are different from the basic rules or targets.
Generally speaking, we classify the user-generated gamemodes into four directions, including the change of game
tempo, the change of game target, the change of game operation, and original game creation. The following part will
discuss the representative prototypes of each direction. (1)The change of game tempo: A typical example is Project
Reality6 from Battlefield 27 , in which the production teamspent 17 years providing content-rich tactical shooters, andthe shortening of TTK provides a different fight experience tothe players. (2) The change of game target: The most notablecase is the aforementioned CS1 . In CS, there are two teams thathave different goals on a closed map, where the terrorists needto plant and detonate a bomb while the Counter-strikers needto stop the terrorists. This user-generated game mode is totallydifferent from Half-Life’s original team deathmatch8 mode. (3)The change of game operation: DOTA2 mentioned above is a
representative example. Originally, the Warcraft III 3 is a realtime strategy (RTS) game, while DOTA changed the modeof controlling an army to only controlling a hero character.
Besides, these directions can also be integrated, as the winninggoal of DOTA is also different from Warcraft III, which canbe regarded as the change of game target. (4) Original gamecreation: This category is somewhat special compared with theprevious game MOD, in which a classic example is Roblox9 .
These games only provide basic rules, environments, materials,
and operations, and players can create new game modes basedon the provided resources, which contains the change of bothgame tempo, game target, and game operation.
B. User-generated Campaigns/Levels
Generally, the developers of games will set some targets orstories for the players to follow. After being familiar with thegames, players may not satisfied with the original storyline andcreate new levels, new campaigns, or new explorable content.
This kind of UGC possibly introduces new art, music, map, ormodel resources, but they will not change the original gamemode and basic rules. This is a very common type of UGC invideo games, especially for the games with map editors.
Regarding to the user-generated campaigns/levels, first ofall, we consider they should be complete as campaigns/levels,
which means they may have an independent portal rather than
only a small piece of object in the base game. For example,
5 https://www.smilegate.com/en/game/crossfire.do
6 https://www.realitymod.com/
7 https://www.ea.com/games/battlefield/battlefield-2
8 https://en.wikipedia.org/wiki/Deathmatch
9 https://www.roblox.com/

Fig. 1. Decision tree-like classification Venn diagram of user-generated content and the corresponding editors in video games.

in Minecraft10 , if the players created a building and moved it
into their archive, it will not be counted as a user-generated
campaign/level since it’s too small and doesn’t have a separate
portal. But, if the players generated a whole map around thebuilding with a corresponding storyline and game target, it
will be regarded as a user-generated campaign/level, sinceother players could load the map individually through thegame’s level selection and explore the map. Second, the usergenerated campaigns/levels should not change the game modeof the base game itself, such as a MOD of Hearts of Iron IV 11
named The New Order: Last Days of Europe (TNO)12 , whichbuilt a completely different world and history from the original
game, and added a lot of external art and music resources,
but TNO did not change the basic game mode of the original
Hearts of Iron IV. Therefore, we still regard the TNO as auser-generated campaign/level of Hearts of Iron IV.
According to our survey, we find that the user-generated
campaigns/levels mainly come from two sources: (1) Buildin map editor: There are many games that provide build-in
map editors for players to customize the original environment.
For example, Age of Empires II: The Conquerors13 , Super
Mario Maker14 , Forza Horizon 515 , etc, provide in-game map
editors for players to create new levels. (2) External gameresource modification: Some games equip with external gameeditors, which could modify outside resources to change thecampaigns/levels, also known as modification (MOD). The
aforementioned TNO and The Elder Scrolls V: Skyrim’s16 story
MOD The Forgotten City17 are both outside MODs. More
10 https://www.minecraft.net/
11 https://www.paradoxinteractive.com/games/hearts-of-iron-iv/about
12 https://steamcommunity.com/sharedfiles/filedetails/?id=2438003901
13 https://www.ageofempires.com/
14 https://supermariomaker.nintendo.com/
15 https://www.xbox.com/en-US/games/forza-horizon-5
16 https://elderscrolls.bethesda.net/en/skyrim
17 https://forgottencitygame.com/

famously, the notable CS map DUST2 also belongs to usergenerated campaigns/levels, which started as a map MODthat can be downloaded from forums and then was officiallyincorporated into the game due to its great reputation.
C. User-generated Resource Files
In some games, the users need to directly modify the gamefiles or resources to create UGC. The well-known MODs invideo game community refer to these user-generated resource
files and feature new files imported from outside of thegame. Common forms of user-generated resource files include
modifying art resources, audio resources, action resources,
new items, new characters, new weapons, and so on. It is
worth mentioning that if the added resource is a separate map,
we will regard it as a user-generated campaign/level, which
is discussed in Sec. III-B. Therefore, in our consideration,
the user-generated resource files are usually small items thatneed to modify the original resources to achieve the players’
goal. For example, there is a suit of clothing for engineers in
the original game, but the user privately change it to a suitfor fishing by modifying the resource file, which would be
regarded as the user-generated resource files.
Since the user-generated resource files are MODs imported
from outside of the game, there is basically no official production tool. On the other hand, creating these UGC needs
to analyze the source codes of the game, which is morecommon in open-source games such as Half-life3 . Therefore,
the threshold of producers for creating the user-generated
resource files is relatively high, since they need to have theability of programming. However, although there are not many
creators that have these abilities and skills, the players who arereally willing to make this kind of UGC are basically the core
players who love the game deeply. Generally, these players
are more likely to produce high-quality UGC, which is highly
beneficial for the development of UGC in the game. However,with the game developers increasingly focusing on official

editors, the number of creators struggling for user-generated
resource files is decreasing compared with other categories.
As mentioned above, the production of the user-generated
resource files needs to analyze and modify the original gamefiles, so not all game companies are willing to allow players
to do so. For example, Rockstar Games18 , the maker ofthe notable Grand Theft Auto series, seems an opponent of
the MODs in their published games. Although the MODsof Grand Theft Auto V are really abundant and impressive,
including various vehicles, characters, etc, Rockstar Games
explicitly prohibit the modification of Grand Theft Auto V 19 intheir End User License Agreement20 . On the contrary, VALVE
Corporation21 , the maker of Half-life series, actively discloses
the source code to encourage creators to make new MODs fortheir games. Moreover, due to the popularity of CS, VALVE
even acquired the production team of CS and supported themto develop CS independently which became famous video
games around the world, and so did Day of Defeat22 . In thispaper, we do not intend to compare the solution and attitudeof game companies toward the user-generated resource files,
since some MODs may break the balance of competition in
multi-player games (so-called plug-in) or even violate policies
and cause legal issues, which would be harmful for the games
and companies. In most cases, the useful and interesting gameMODs are very important and show a highly positive impact
on the game community, which also fosters many good gameproducers who were MOD creators before their formal work.
D. User-generated Game Objects
The user-generated game objects are most common UGC invideo games. The players can use the provided game editors
to create the UGC of game objects without importing outside
resources. The creation of the user-generated game objects has
the simplest threshold compared with other categories, sincemost of the creation approaches are bound to the games’ own
play mode, so the players do not need to learn extra operationand logic. This is the most intuitive way for normal users
to feel the sense of achievement when creating UGC, which
activates the players’ innovation ability and also extends thegames’ life cycle. But correspondingly, this creation approachshows great limitations and low degree of freedom during
the editing. For example, many games only allow players tocustomize the color scheme of characters, while not truly allow
them to change their models, actions, or audio, etc.
The user-generated game objects exist in many notable
games. For example, in Escape from Tarkov23 , players canmodify their weapons as they wish. In Besige24 , players canfreely construct their favorite machines to bit against castles orarmies. Sports games also allow the users to customize teammembers, e.g. Pro Evolution Soccer25 allows users to create
new players by setting their ratings, faces, actions, etc. Moresimply, the players can just paint the characters to shows theirpersonality in Human: Fall Flat26 .
On the other hand, the sandbox games are special cases.
Many sandbox games or physical simulation games (e.g.,
Minecraft8 , The Sandbox27 , Cryptovoxels28 , etc) do not set
clear game targets, while they provide platforms for theplayers to create UGC. Although these sandbox games havea powerful degree of freedom and creation potential, mostcommon players might only use them to create some small
customized items, like a house, a tree, a piece of furniture, etc.
Therefore, we regard this kind of UGC as user-generated gameobjects, while the huge and elegant scenes will be classified
as user-generated campaigns/levels discussed in Sec. III-B.
IV. C ATEGORIES OF U SER -G ENERATED C ONTENT E DITOR
In the previous section, we discuss the classification of
the UGC in video games. Correspondingly, we also builda decision tree-style classification Venn diagram for UGC
editors as shown in Fig. 1, which contains four types, including
level editors, gameplay editors, game editing engines, andcommunity-made game editors. The details of the UGC editors
will be discussed in the following subsections.
A. Level Editors
To enhance the playability and longevity of video games,
many existing products allow users to customize campaigns/levels. This kind of UGC editor usually does not allow
users to create new rules that are different from the base game,while only allowing players to use existing elements to makenew levels based on the basic rules of the games. With level
editors, players can only expand the gaming experience rather
than enhance the experience or create a new experience, and
it is a great way for the players to extend the lifespan ofa game by themselves. Majority of the official game UGC
editors falls into the level editors, especially in the early daysof video games, e.g. console-based games like the NintendoEntertainment System (NES)29 and Sega Genesis30 , in which
the players can only modify or optimize a small part of thecampaigns/levels due to the limitation of the hardware.
Currently, many modern games make it much easier toimplement the level editors instead of other more complex
editors that can change the game rules, so most existing
notable video games officially provide level editors with thebase games. For example, the editor in the early NES game
Excite Bike only allows players to re-permutate the pre-madeobstacles to create new levels, which is a small extension
based on the original game without breaking any existing rules.
Specifically, level editors have enormous popularity in RTS

18 https://www.rockstargames.com/
19 https://www.rockstargames.com/gta-v

25 https://www.konami.com/wepes/2021/us/en-us/ps4/

20 https://www.rockstargames.com/eula?country=us

26 https://www.nobrakesgames.com/humanfallflat

21 https://www.valvesoftware.com/

27 https://www.sandbox.game/en/

22 https://www.dayofdefeat.com/

28 https://www.cryptovoxels.com/

23 https://www.escapefromtarkov.com/?lang=en

29 https://www.nintendo.com/nes-classic/

24 https://www.spiderlinggames.com/

30 https://genesismini.sega.com/

games, like Warcraft III: Frozen Throne, StarCraft II: Wings ofLiberty31 , Age of Empires II: The Conquerors, etc. Moreover,many FPS games also provide level editors and contributeto sustain the improvement of the games, e.g. DOOM 32 andHalo333 . Specifically, we can find that the players’ reactions
to these UGC in DOOM are highly positive, since the MOD
communities of DOOM are still active even thought DOOM
was developed about 30 years ago, such as MODDB34 .
B. Gameplay Editors
Gameplay editors denote the UGC editors that can create
new rules (or break existing rules) different from the original
games. The gameplay editors not only allow players to use
existing elements in the games’ levels but also to change therules to make new content. In this paper, we name this kind of
editor as gameplay editors since the created UGC is possibly
not limited to the original game, so the created UGC cancompletely abandon the original rules and even make a new
game based on the basic elements. With gameplay editors,
players can have more freedom than level editors, which may
be helpful for building a long-lasting creator community andexpanding the longevity of the games with endless creativity.
Gameplay editors are getting more and more popular today.
For example, the most recently renowned one is the editor
in the AAA (3A) game titled Battlefield 204235 . With thisgameplay editor, players managed to create a “squid game”
mode based on the famous Korean TV play, which represents
the high potential and freedom of gameplay editors. Moreover,in the gameplay editor of Overwatch36 , an FPS game, theplayers can use the resources provided by the gameplay editor
and its rich customization tools to create games in completely
different genres such as a 2D platform game (often simplified
as platformer or jump and run games, e.g. the early version
of Super Mario Bros), hide-and-seek, zombie mode, etc.
By comparison, the high potential of gameplay editors alsocomes with high development costs due to the complexity ofcreating those editors. Basically, the development workload
almost equals to developing an in-game editing engine, which
explains why gameplay editors are more commonly seen in
3A titled games instead of indie titled games. On the other
hand, the gameplay editors also come with the limitation of theoriginal game’s resources. Generally, most official gameplay
editors will provide ways for creators to spread their UGC
to other players in the game. So, in an official game editor,
players usually cannot import their external resources into thegame due to the developer’s consideration of the legibility andpotential copyright issue of the external resources and files.
C. Game Editing Engines
Different from the gameplay editors, game editing engines
have richer features compared with the gameplay editors,
31 https://starcraft2.com/
32 https://bethesda.net/en/game/doom
33 https://www.halowaypoint.com/en
34 https://www.moddb.com/games/doom/mods

like real game engines. Specifically, we consider the maindifference that separate game editing engines and gameplay
editors is the external resource. Game editing engines canbring assets from outside of the game to make brand newcontent that look completely different from the base games,
while the gameplay editors only allow creators to use assets
within the game. Sometime, those UGC can be new gamegenres or even be made as a standalone game. Both the Battle
Royale [26] mode and MOBA are started as UGCs created insuch game editing engines. For example, DOTA was createdusing Warcraft III’s game editing engine, which was further
developed as a standalone game separate from the base game.
Another difference between game editing engines and gameplay editors is that the content created in game editing engines
are not officially distributed in the game by the developer due
to the copyright concern from the external assets imported by
the creators. Thus, the UGC created by game editing engines
are normally distributed by the creators themselves as theform of MODs. For instance, some variations of DOTA are
distributed by the player community, and the players can playthem using the official Battle.net37 server or using the local
area network (LAN) to connect with each other.
Specifically, a small quantity of UGC is made using gameediting engines but also is distributed by the developers. For
example, in Roblox Studio38 , a game editing engine of Roblox,
players can make their custom assets. Even though Roblox
Studio basically does not provide base game content, thestrong capability of its game editing engine gives Roblox
more and more UGC over the last 10 years. But, it is worth
mentioning that the UGC created by Roblox Studio will becensored before it can be distributed to the players, and thestrict copyright system guarantees the quality of UGC in
Roblox. Correspondingly, the system of Roblox also costs a
certain degree of the workload for its developers and operators.
Though a game editing engine is much harder to construct andmaintain than a game editor or a level editor, the amount andquality of the UGC can also achieve a higher level. According
to the experience of Roblox Studio, we consider the gameediting engine may be the most ideal tool for game UGC.
D. Community-made Game Editors
As discussed in Sec. III-C, many game companies do
not provide official game editors because of many different reasons, e.g. legal considerations, corporate culture, etc.
Therefore, many professional players in game communities
would develop non-official game editors for modifying andcreating content of the games, which are called communitymade game editors in this paper. The core difference between
community-made game editors and official game editors is themaintenance, which means the community-made game editors
are created and maintained by the player community without
the participation of the official game developers.
Most community-made game editors change the games
through integrating MODs to the original games, including

35 https://www.ea.com/games/battlefield/battlefield-2042

37 https://www.blizzard.com/en-us/apps/battle.net/desktop

36 https://playoverwatch.com/en-us/

38 https://www.roblox.com/createbut not limited to changing the player states, modifying gameobjects’ models, adding new maps, creating customized gamemodes, etc. The community-made game editors mainly rely
on modifying game files by the players, which are mostly
available on personal computers (PCs) rather than consoles.
Although there are MODs and corresponding editors on
hacked versions of consoles, these editors often have higher
threshold. Thus, compared with the previous three kinds ofeditors, community-made game editors are only designed fora small proportion of enthusiasts to customize their favorite
games. More importantly, it is common that only the populargames can have a dedicated community to make various kindof editors, and the abundant editors also play an importantrole in extending the game life-span, which builds a positive
circulation for the popular games at the same time.
The most common kind of community-made game editorsthat can be seen in most PC game is trainers, which could
modify memory values of games based on memory addresses.
For example, a community-made editor of Pro Evolution Soccer allows users to adjust the player ranking, club transferring,and player value, etc. Another kind of popular communitymade game editors is model swapper, which allows players
to swap the in-game models of game objects (e.g. changing
the model of the main character). For instance, in Grand
Theft Auto V, players can use swapper to change the modelof characters, passers-by, vehicles, etc. Moreover, there aresome community-made game editors allow players to havefull control of the camera and adjust its angle to have a betterview of the game world and even record cinematic videos.
For example, players made a plug-in for Resident Evil 239 tochange the field of view (FOV) of camera, introduce manual
flashlight, and allow players to swap characters/outfits.
V. P ROPAGATION OF U SER -G ENERATED C ONTENT
To build a positive circulation of UGC in video games,
the propagation of UGC plays a necessary role through lotsof approaches, like player community sharing, circulation in
trading markets, combination with original games, etc. The
following subsections will discuss these methods.
A. Player Community Sharing
Sharing in the player community is a common way to spreadthe game UGC, which we consider is the most widespread andfast way for UGC propagation. For the area of video game,the player community mostly refers to the online forum andchatting group for players to share their gaming experience,
gaming strategies, etc. The motivation of player community
sharing mainly comes from two perspective: (1) It comes fromthe true affection of the base games. The sharing of highquality UGC in the player community may raise a certain
degree of attention and attract more players to join the game,
which could motivate more creation of UGC based on the
popular one, and the participation of more players also drives
the game companies to constantly maintain the game. (2) It

comes from the popularity and competition of the creators in
UGC communities. The spread of UGC could meet the needsof UGC creators for sharing their ideas and creations withother players, enriching the emotional experience of creators,
and generating a certain incentive for the UGC creators. On theother hand, the player community is the most intuitive way forcommunicating with the UGC creators, which could build apositive feedback about the UGC and help their improvement.
There are many notable examples of UGC that were famous
for the sharing in the player community. For example, anotable Warcraft III battle map named Chenghai 3C40 enjoyedequal popularity with DOTA in early years, which was uploaded on online forum and then propagated in chatting groups
and LAN. Besides, in lots of large online game communities
like Modyolo41 and apkmody42 , the players would freely
upload their created MODs, patch resources, and even selfmade editors for other players to use and share.
B. Circulation in Trading Markets
In some games, a part of the UGC mainly focuses onbuilding a unique appearance or special usability, which has
a strong appeal to some players, so the circulation in the
trading market becomes one of the main ways for this UGC
propagation. UGC circulation in the trading market means thatUGC creators can trade their creations on online platforms
for economic consideration, and players would buy the UGC
according to their preference for the UGC’s practical value,
collection value, reputation, etc. Therefore, the two sides inthe trading market can build the UGC transactions to achieve
the ultimate effect of mutual benefit and a win-win. Oneof the trading methods is on the game’s officially available
UGC trading platform (e.g. The Sandbox Shop43 ), where UGC
creators and the game players can trade the UGC certified on
the official platform. Another way to trade UGC between users
is peer-to-peer (P2P) transactions, where UGC creators andbuyers can connect each other using third-party platforms.
Representative examples of circulation in the marketplace include The Sandbox Shop, Cryptovoxels Marketplace44 ,Steam Workshop45 , etc. In The Sandbox Shop, players cantrade user-generated entities, equipment, wearables, avatars,
etc. Similarly, wearables, voxel artworks, and customized
objects can be built in Cryptovoxel and traded in Cryptovoxels
Marketplace. More importantly, these transactions will be
confirmed on blockchain to guarantee the ownership of thedigital assets, which will be further discussed in Sec. VI.
Moreover, Steam Workshop may be the most common UGC
trading market, which is a central hub of player-created content
and tools to publish, organize, download, and trade UGC for
corresponding games. Specifically, for the games created by
VALVE (e.g. Counter-Strike: Global Offensive (CS: GO)1 ),40 http://www.ch3c.cn/
41 https://modyolo.com/
42 https://apkmody.io/
43 https://www.sandbox.game/en/shop/
44 https://www.cryptovoxels.com/marketplace

39 https://www.residentevil2.com/us/

45 https://steamcommunity.com/workshop/

Steam Workshop would encourage the players to create UGC
and publish them freely, and VALVE will share out bonuses
according to the popularity and voting of these UGC.
C. Combination with the Original Games
Through the official UGC creation platform, players cancreate various UGC with their imagination and creativity,
like unique game levels with higher playability and different
gaming experience. For outstanding UGC, the official developers may integrate these UGC with the original game toextend them as a part of the game. In this way, UGC canbe used and appreciated by more players, which not only
efficiently utilizes the innovation of the UGC creators but also
increases the richness and diversity of the game content andconstantly attract the players of the game. From the perspectiveof creators, the official certification can also motivate them tobuild high-quality UGC. Therefore, the combination of UGCwith the original games is also a promising method for UGC
propagation and development in video games.
For the combination of UGC and original games, VALVE
can be a representative leader. Specifically, the most famouscase is the integration of CS and player-made maps. In theearly version of CS, the map DUST2 was a user-generated mapthat was famous around online communities. In the subsequent
releases, the map DUST2 was officially integrated into CS andalso spread to other FPS games later, which makes it highly
notable that almost all FPS players are familiar with the map
DUST2, even though they might not be original players of
CS. Another example is Team Fortress 246 , a cartoon-like FPS
video game developed by VALVE. In 2013, Team Fortress2 added the first community-made update, named Robotic
Boogaloo47 , which contained 57 new items including in-gamecontent, the update hub website, the animated short, the comic,
and the splash images in the Steam store.
VI. V ISION OF U SER -G ENERATED C ONTENT
With the development of network capacity, physical engine, and computational power, the video game will show agreat improvement beyond the scope of entertainment, andwe believe the final form of the video game is metaverse.
Metaverse denotes the next-generation Internet in which users
can control their avatars to interact with other users andsoftware applications in a 3D virtual space [27]. Different fromthe common video games, in metaverse, there are no specifictargets for players to chase, while the players can freely playfor entertainment, creation, and even work. Theoretically, themetaverse has unlimited extension space for UGC creationand seamless scene transformation, so the construction of
metaverse will highly depend on the users’ creativity andinnovation [27]. Therefore, we believe the creation, artisticstyle, behavior, culture, and economy of UGC in metaverse
will be significantly promising research areas, and we conclude
two representative directions in the following subsections.

A. Evolution of User-Generated Content Editors
For promoting the UGC creation, the most intuitive requirement is an efficient UGC editor/tool that could facilitate thecreation procedure and lower the threshold for all new players.
Although there is multiple existing 3D modeling software (likeMaya48 , Blender49 ), and UGC editors discussed in Sec. IV,
most existing editors are highly dependent on professional
knowledge and practical experience, so it is difficult for new
players to use. Therefore, it is imperative to make breakthroughs for the evolution of UGC editors/tools.
In recent years, AI-related technologies have shown great
improvements, especially in content generation (e.g., generative adversarial network (GAN) [28]). With the help of GAN,
it is easier for new players to create beautiful pictures withhandy sketches [29] and fine-grained models by low-resolution
models [30], so the integration of game UGC editors and
GAN is a potential trend for improving the UGC editors.
Moreover, procedural content generation (PCG) can also be ahelpful solution [31]. The UGC editors can provide PCG-based
modules to help creators to construct the virtual environment(e.g., buildings, trees, grasses, plants, mountains, planets, etc).
Specifically, we also need to point out the impact of artisticstyle in UGC creation, especially voxels. The voxel style has
shown a great potential for UGC creation in many populargames (e.g., Minecraft, Cryptovoxels, Lego Worlds50 , etc).
Compared with other artistic styles, the voxel style has its
special advantages: (1) Voxel style objects are quite simple
and intuitive for UGC creation and modification with low
learning cost; (2) Most voxel style avatars are abstract, so theuncanny valley problem may be effectively avoided; (3) The
voxel style modeling can unlock new simulation techniques(e.g. simulation of smart materials [32]), which is hard forother modeling methods. Therefore, in our vision, we consider
the voxel style may be the mainstream in future metaverse applications, and the corresponding problems of voxel modelinglike the physical engine (e.g. collision, fragmentation, etc) andAI-assisted UGC generation will be promising research topics.
B. Ownership and Economy of User-Generated Content
The economic system is necessary for a large-scale virtualworld, also known as a virtual economy [33]. With the development of blockchain-related technologies, the decentralized
finance (DeFi) with the digital currency of ERC-20 Token
Standard51 can be naturally helpful for building the economic
system of the metaverse. Moreover, ERC-721 Non-Fungible
Token (NFT) Standard52 can certify the digital assets as uniqueand not interchangeable tokens on the blockchain, whichmeans the UGC in video games could truly belong to theusers while not depend on the operating companies of thegames. Under this circumstance, the UGC in video games cantruly have specific values as NFTs rather than only represent
48 https://www.autodesk.com/products/maya/overview
49 https://www.blender.org/
50 https://www.lego.com/en-gb/categories/games/lego-worlds

46 https://www.teamfortress.com/

51 https://ethereum.org/en/developers/docs/standards/tokens/erc-20/

47 https://wiki.teamfortress.com/wiki/Robotic Boogaloo

52 https://eips.ethereum.org/EIPS/eip-721

abstract feelings or enthusiasm for the game, and the valuesof the UGC may depend on multiple factors, such as their
quality, scale, rarity, iconic meaning, creators’ fame, etc.
Moreover, the online markets of both official marketplace(e.g. Cryptovoxels) and third-party exchange (e.g. Opensea53 )will provide liquidity for UGC. On these platforms, players
can freely select their preferred digital assets, and creators
can build objects with higher quality to earn higher rewards.
Thus, a creator economy ecosystem with positive circulationis built, in which the players will have higher user stickinessdue to their favorite UGC and the corresponding cost, and thenotable creators also become the builders of the metaverse who
can earn for life like the architects in the real world. And thisexciting UGC creator economy will attract more participantsof both creators and players, thus enhancing the ecosystemagain. Therefore, the study of the blockchain-based creator
economy is necessary for the further improvement of the UGC.
VII. C ONCLUSION
In recent years, UGC has gradually become an importantfeature and component of outstanding video games, and in
the future, UGC will play a more necessary role in building
the metaverse. This paper reviews and classifies the existing
UGC and the corresponding editors, and lists the propagation
approaches of UGC. More importantly, this paper proposes
our vision for the development of UGC, which focuses on thepromising prospects and research directions in the metaverse,
including the evolution of UGC editors and the ownership andeconomy of UGC. We believe the prosperous game industry
will benefit from the creativity and innovation of UGC, andthe forms, values, and meanings of UGC will also achieve ahigher level during the building of metaverse.
ACKNOWLEDGMENT
This work was supported by Shenzhen Science and Technology Program (Grant No. JCYJ20210324124205016).
R EFERENCES[1] T. Min, H. Wang, Y. Guo, and W. Cai, “Blockchain games: A survey,”
in 2019 IEEE conference on games (CoG). IEEE, 2019, pp. 1–8.
[2] T. K. Naab and A. Sehl, “Studies of user-generated content: A systematic
review,” Journalism, vol. 18, no. 10, pp. 1256–1273, 2017.
[3] Z. Zhao, N. Laga, and N. Crespi, “A survey of user generated service,”in 2009 IEEE International Conference on Network Infrastructure andDigital Content. IEEE, 2009, pp. 241–246.
[4] J. Lundmark and E. Sandström Lindberg, “The effects of intrinsic
motivation, extrinsic motivation and toolkits onuser participation in usergenerated content for video games:: A quantitative study of productdevelopment in online communities,” 2015.
[5] O. Sotamaa and H. Wirman, “Online games modifications and user
generated content,” The International Encyclopedia of Digital Communication and Society, pp. 1–10, 2015.
[6] V. Kasapakis and D. Gavalas, “User-generated content in pervasive
games,” Computers in Entertainment (CIE), vol. 16, no. 1, pp. 1–23,
2017.
[7] R. L. S. Dı́az, G. R. Ruiz, M. Bouzouita, and K. Coninx, “Building
blocks for creating enjoyable games—a systematic literature review,”
International Journal of Human-Computer Studies, p. 102758, 2021.
[8] J. Krumm, N. Davies, and C. Narayanaswami, “User-generated content,”
IEEE Pervasive Computing, vol. 7, no. 4, pp. 10–11, 2008.
53 https://opensea.io/[9] C. Wyrwoll, “User-generated content,” in Social Media. Springer, 2014,
pp. 11–45.
[10] X. Ochoa and E. Duval, “Quantitative analysis of user-generated content
on the web,” 2008.
[11] A. Estrella-Ramón and F. Ellis-Chadwick, “Do different kinds of usergenerated content in online brand communities really work?” Online
Information Review, 2017.
[12] G. Christodoulides, C. Jevons, and J. Bonhomme, “Memo to marketers:
Quantitative evidence for change—how user-generated content reallyaffects brands,” Journal of advertising research, vol. 52, no. 1, p. 53,
2012.
[13] D. C. Ukpabi and H. Karjaluoto, “What drives travelers’ adoptionof user-generated content? a literature review,” Tourism management
perspectives, vol. 28, pp. 251–273, 2018.
[14] A. Barreda and A. Bilgihan, “An analysis of user-generated content
for hotel experiences,” Journal of Hospitality and Tourism Technology,
2013.
[15] M. T. Cuomo, D. Tortora, A. Giordano, G. Festa, G. Metallo, andE. Martinelli, “User-generated content in the era of digital well-being:
A netnographic analysis in a healthcare marketing context,” Psychology& Marketing, vol. 37, no. 4, pp. 578–587, 2020.
[16] M. Luca, “User-generated content and social media,” in Handbook of
media Economics. Elsevier, 2015, vol. 1, pp. 563–592.
[17] G. Lastowka, “User-generated content and virtual worlds,” Vand. J. Ent.
& Tech. L., vol. 10, p. 893, 2007.
[18] C. S. Brunt, A. S. King, and J. T. King, “The influence of user-generated
content on video game demand,” Journal of Cultural Economics, vol. 44,
no. 1, pp. 35–56, 2020.
[19] A. Liapis, G. N. Yannakakis, and J. Togelius, “Sentient sketchbook:computer-assisted game level authoring,” 2013.
[20] G. Ng, J. G. Shin, A. Plopski, C. Sandor, and D. Saakes, “Situated gamelevel editing in augmented reality,” in Proceedings of the Twelfth International Conference on Tangible, Embedded, and Embodied Interaction,
2018, pp. 409–418.
[21] M. Davidovici-Nora, “The dynamics of co-creation in the video gameindustry: the case of world of warcraft,” Communications & Strategies,
no. 73, p. 43, 2009.
[22] A. Summerville and M. Mateas, “Super mario as a string: Platformer
level generation via lstms,” arXiv preprint arXiv:1603.00930, 2016.
[23] M. Guzdial and M. Riedl, “Game level generation from gameplay
videos,” in Twelfth Artificial Intelligence and Interactive Digital Entertainment Conference, 2016.
[24] M. Guzdial, N. Liao, J. Chen, S.-Y. Chen, S. Shah, V. Shah, J. Reno,
G. Smith, and M. O. Riedl, “Friend, collaborator, student, manager: How
design of an ai-driven game level editor affects creators,” in Proceedingsof the 2019 CHI conference on human factors in computing systems,
2019, pp. 1–13.
[25] S. Heintz and E. L.-C. Law, “The game genre map: A revised game classification,” in Proceedings of the 2015 Annual Symposium on ComputerHuman Interaction in Play, 2015, pp. 175–184.
[26] G. Choi and M. Kim, “Gameplay of battle royale game by rules andactions of play,” in 2018 IEEE 7th Global Conference on Consumer
Electronics (GCCE). IEEE, 2018, pp. 599–600.
[27] H. Duan, J. Li, S. Fan, Z. Lin, X. Wu, and W. Cai, “Metaverse for social
good: A university campus prototype,” in Proceedings of the 29th ACM
International Conference on Multimedia, 2021, pp. 153–161.
[28] I. Goodfellow, J. Pouget-Abadie, M. Mirza, B. Xu, D. Warde-Farley,
S. Ozair, A. Courville, and Y. Bengio, “Generative adversarial nets,”
Advances in neural information processing systems, vol. 27, 2014.
[29] W. Chen and J. Hays, “Sketchygan: Towards diverse and realistic
sketch to image synthesis,” in Proceedings of the IEEE Conference on
Computer Vision and Pattern Recognition, 2018, pp. 9416–9425.
[30] Z. Chen, V. G. Kim, M. Fisher, N. Aigerman, H. Zhang, and S. Chaudhuri, “Decor-gan: 3d shape detailization by conditional refinement,”in Proceedings of the IEEE/CVF Conference on Computer Vision and
Pattern Recognition, 2021, pp. 15 740–15 749.
[31] J. Liu, S. Snodgrass, A. Khalifa, S. Risi, G. N. Yannakakis, andJ. Togelius, “Deep learning for procedural content generation,” NeuralComputing and Applications, vol. 33, no. 1, pp. 19–37, 2021.
[32] G. Sossou, F. Demoly, H. Belkebir, H. J. Qi, S. Gomes, and G. Montavon, “Design for 4d printing: Modeling and computation of smart
materials distributions,” Materials & Design, vol. 181, p. 108074, 2019.
[33] M. Nazir and C. S. M. Lui, “A brief history of virtual economy,” Journal
for Virtual Worlds Research, vol. 9, no. 1, 2016.