Game accessibility
Within the field of human–computer interaction, game accessibility refers to the accessibility of video games.   More broadly, game accessibility refers to the accessibility of all gaming products, including tabletop RPGs and board games.  Video game accessibility is considered a sub-field of computer accessibility, which studies how software and computers can be made accessible to users with various types of impairments.

With an increasing number of people interested in playing video games and with video games increasingly being used for other purposes than entertainment, such as education, rehabilitation or health, game accessibility has become an emerging field of research, especially as players with disabilities could benefit from the opportunities video games offer the most. A 2010 study estimated that 2% of the U.S. population is unable to play a game at all because of an impairment and 9% can play games but suffers from a reduced gaming experience. A study conducted by casual games studio PopCap games found that an estimated one in five casual video gamers have a physical, mental or developmental disability. As games are increasingly used as education tools, there may be a legal obligation to make them accessible, as Section 508 of the Rehabilitation Act mandates that schools and universities that rely on federal funding must make their electronic and information technologies accessible. As of 2015, the U.S. Federal Communications Commission (FCC) requires in-game communication between players on consoles to be accessible to players with sensory disabilities.

Barriers to access 

Video game accessibility problems can be grouped into three categories that correlate to a specific type of impairment:
Not being able to receive feedback from the game due to a sensory impairment. Examples include: not being able to hear dialogue between game characters or audio cues, such as an explosion, because of a hearing impairment or unable to see or distinguish visual feedback, such as different colored gems in a puzzle game due to a visual impairment such as colorblindness.
Not being able to provide input using a conventional input device due to a motor impairment; for example, users who rely upon using switch controller or eye trackers to interact with games may find it very difficult or impossible to play games that require large amounts of input.
Not being able to understand how to play the game or what input to provide due to a cognitive impairment. People with learning disabilities may have low literacy or a combination of complex needs, for instance an individual might also have Ataxia or limited coordination. For example, real-time strategy games require a lot of micromanagement, which may be too difficult to understand and to perform for someone with a learning impairment.

Government regulations

United States
In the US, the 21st Century Communications and Video Accessibility Act 2010 (CVAA) brought up-to-date accessibility guidelines to advanced communication services (ACS), which is considered to include video games with communication elements including text and voice chat and the user interface (UI) elements to reach the chats. Video game trade groups including the Entertainment Software Association have requested waivers of CVAA enforcement for video games, arguing that while there is strong interest in the video game community to provide accessibility, video games are first and foremost for entertainment and not for communication, and that because of the complexity of video game software, there are few standardized solutions compared to other ACS platforms.

The Federal Communications Commission granted a final waiver that expired on December 31, 2018, making all video games developed and released after January 1, 2019 expected to be compliant with the CVAA; games that were partially developed after January 1, 2019 are expected to reasonably meet the CVAA compliance, as well as any game that issues major updates after that date. The FCC would hear consumer complaints about games that failed to meet the CVAA, determine how feasible the remedy would be, and then determine if they should issue fines against the publisher of the game title.

Accessible game categories 

Over the past decade, small companies and independent game developers have developed numerous games that seek to accommodate the abilities of players with the most severe impairments and which has led to the definition of the following accessible game categories:
Audio games are games specifically for gamers who are blind. These games can be played without visual feedback and instead use audio-based techniques such as audio cues or synthetic speech. The audiogames website provides a comprehensive overview of available games.
One-switch games are games that can be played using switch access and which accommodate the abilities of users with severe motor impairments or cognitive impairments. The oneswitch website provides an overview of available one switch games.
Games for people with a learning disability, people with a Learning disability, may have low literacy or a combination of Complex Needs, for instance an individual might also have Ataxia or limited co-ordination. A  detailed description of gaming with a learning disability.
Universally Accessible games are games that offer multiple interfaces to support different impairments. An overview of universally accessible games can be found here.

These games are not only great examples of accessible games, but also drive innovation in game design. In recent years, game accessibility has been actively researched, for example in student projects
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The unique limitations of the target group make such projects interesting, instructive and challenging for students.

Modifications for improved accessibility

Controllers 
Small companies and volunteer based groups have modded video game controllers to help make video games more accessible for those with physical impairments.

 Game Box Controllers are modified XBox, XBox 360, Playstation 3 controllers, with different switches and are custom to the needs of the individual, with much variety.
 Ben Heck modifies XBox One controllers to be able to function single handedly.
 The Controller Project is a volunteer based project where people can request or build custom controller modifications to better other's gaming experiences.
 SpecialEffects is a UK based charity where therapist and technologists modify game controllers and eye motion software to help better the accessibility for games for people with impairments.
 Console Tuner is a piece of equipment which lets the player use their preferred controller (XBox, Playstation, Wii, Mouse & Keyboard) on compatible systems.

Strategies for improving accessibility

There have been several attempts at composing a set of game accessibility guidelines similar to the Web Content Accessibility Guidelines.

Guidelines by advocacy organizations
The International Game Developers Association (IGDA) Special Interest Group on Game Accessibility proposed 19 accessibility guidelines in 2004, which were derived from a survey of 20 accessible games. The majority of the games surveyed include games for the visually impaired, and several support motor or hearing impaired gamers.

The Norwegian Medialt organization published a set of 34 game accessibility guidelines on their website, based on the 19 IGDA game accessibility SIG guidelines as well as their own set of guidelines.

2012 saw three major launches, Best Practices in Video Games in April 2012 by CEAPAT, Game Accessibility Guidelines in September 2012 by a group of developers, specialists and academics, and Includification, also in September 2012, by AbleGamers.

In 2019, AbleGamers launched Accessible Player Experience APX, to increase the number of accessibility experts in AAA studios, as part of their new website accessible.games. APX focuses on provided an equal play experience without making designers feel restricted, and adding 'Accessibility Champions' to design teams in large studios.

Strategies from academic research
A general criticism of the guidelines is that they tell a developer what to do but not why or how. An extensive literature survey  of existing accessible games identified a game interaction design model that allows for precisely eliciting how a disability impairs the ability to play a game. Based on this interaction design model three unique types of high-level accessibility barriers can be identified. Based on existing accessible games, the following strategies are proposed to make games accessible: 
Hearing impairment and visual impairment
Enhance stimuli: for example, high contrast color scheme, increased font size, color blind friendly color scheme and zoom options.
Replace stimuli: for example, subtitles or closed captioning, audio cues, sonification, speech synthesis or haptic cues.
Motor impairments
Replace input: for example, support for direct voice input or a brain-computer interface.
Reduce input: for example, switch access scanning and remove or automate inputs.
Cognitive impairment
Reduce stimuli: for example, limit the number of game objects, or simply the storyline.
Reduce time constraints: for example, slow down the game.
Reduce input: for example, remove or automate inputs that needs to be provided.

Advocacy organizations

Several advocacy organizations and groups have been formed to raise awareness within the game industry of the importance of making games accessible.

In 2003, the International Game Developers Association (IGDA) introduced the Game Accessibility Special Interest Group, founded by Thomas Westin. In 2006, the Bartiméus Accessibility foundation initiated the Game Accessibility project, a project which focuses on creating awareness and providing information for game developers, researchers and gamers with disabilities, led by Richard Van Tol. These two major groups work together as advocates within the game industry for increasing the accessibility of video games for gamers with disabilities.

In 2004 two gamers with disabilities, Mark Barlet and Stephanie Walker, founded AbleGamers.com, set out to further advance game accessibility in the AAA gaming space. Some of their efforts include: pressuring NCSoft to remove Game Guard from the game Aion and discussing with game developer Blizzard the addition of color blind friendly enhancements to the game World of Warcraft. In 2009 AbleGamers.com started 501(c)(3) nonprofit The AbleGamers Foundation to facilitate their work.

In 2010 the Accessible GameBase was launched by the charity SpecialEffect. This was a site that aimed to develop a welcoming, all-encompassing gaming community.

In 2012, a group of games studios, specialists and academics came together to create the Game Accessibility Guidelines which won the FCC's Chairman's award for Advancement in Accessibility. This website has many tips for game developers as to how to make their games more accessible to those who have disabilities. They raise awareness about the need for accessibility and the ease of which some features can be implemented.

Despite these, and other initiatives, the situation is far from perfect: Many game developers are still very much unaware of game accessibility. Developers who acknowledge the importance of game accessibility and want to use it in their designs often don't know how to do so. Games developed in research projects usually consist of small demos ("proofs of concept") which lack the quality and (re)playability of mainstream games. This is usually also the case with games that have been developed by small companies and hobbyists. Knowledge about accessible game design that is gained in such projects often fails to get documented. In recent years, game accessibility has become a topic of increasing interest to the academic research community. It is recommended that collaborating with people who have disabilities can vastly improve the results of accessibility initiatives.