A browser game is a video game that is played via the World Wide Web using a web browser. Browser games can be run using standard web technologies or browser plug-ins. The creation of such games usually involves use of standard web technologies as a frontend and other technologies to provide a backend. Browser games include all video game genres and can be single-player or multiplayer. Browser games are also portable and can be played on multiple different devices, web browsers, and operating systems. 
Browser games come in many genres and themes that appeal to both regular and casual players. Multiple browser games have developed beyond the online platform to become large titles or franchises sold physically in stores, in online marketplaces like Steam or XBLA, or in decentralized distribution platforms such as itch.io. Some of those titles are Alien Hominid, Bejeweled, Bloons, Club Penguin, Cookie Clicker, Meat Boy, and Transformice.
Browser games are often free-to-play and do not require any client software to be installed apart from a web browser or browser plug-in. In some cases a game may be free, but charge for extra in-game features. Multiplayer browser games have an additional focus on social interaction, either between several players or on a massive scale. Due to the accessibility of browser games, they are often played in more frequent, shorter sessions compared to traditional computer games.
In 1995, FutureWave Software, wanting to challenge Macromedia's Shockwave program, modified their SmartSketch software by adding frame-by-frame animation tools. The tools were released in FutureSplash Animator for the PC and Macintosh. In December 1996, FutureWave was acquired by Macromedia and the animation editor was renamed Macromedia Flash. This and the release of the ActionScript programming language, were some of the first ways developers made games for browsers. Sun Microsystems also launched a website in 1997 called HotJava that hosted 'applets' which users could run on any browser that ran Java.
One of the earliest popular game websites to run on Java was ClassicGames.com, the largest selection of Java multiplayer games on the Internet, hosting a wide variety of games like Chess, Checkers, and Freecell. It received attention from companies after rapid site growth, such as the number of registered users on the site jumping from 50,000 to 60,000 in November to December 1997. It was bought out by Yahoo! in 1998 and turned into Yahoo! Games. Vice claims that Yahoo! Games most likely had an impact on the "online poker boom of the early 2000s" as it was one of the first websites to host the game in 1997, predating PlanetPoker which started in 1998. In 1996, Microsoft acquired the small online gaming site "The Village". The site was relaunched under the "Internet Gaming Zone" branding at zone.com. It first hosted card and board games similar to Yahoo! Games. While acclaimed by the Los Angeles Times in 1997, they also called the site "more complicated than necessary" because users had to download more than 3 megabytes of special software to play the games, and because only Internet Explorer could run the site. It would be renamed many times over the years, to "Microsoft Zone", "MSN Games" and others. A notable series that came out of Microsoft Zone was Bejeweled.
Digital Trends writes that many early Flash games were browser-based recreations of classic video games like Pac-Man or Frogger, and the market grew with the introduction of higher-speed Internet connections. Toby Rowland of the casual game site King.com said in 2007, "Broadband penetration is one of the big drivers on the industry and the other is the advance in quality of Flash technology itself". Some of the more notable websites for flash games were Newgrounds, AddictingGames, Miniclip, and Kongregate. Developers often made flash games because of a model where they were free demos to full games that would come out later, and also because they could create more experimental games than could be allowed onto consoles. Flash games went viral through the use of AIM and e-mail.Humongous Entertainment was a developer that lost players to Flash games in the early 2000s.
In 1996, Tom Fulp developed the games "Club a Seal" and "Assassin" for his Neo Geo fansite New Ground. A year later, after making the sequels to both games, he made a separate site, Neo Geo Atomix, specifically for hosting browser games. In 1998, Fulp began experimenting with Macromedia Flash, and combined both websites into Newgrounds. By 1999, there was considerable traffic on Newgrounds. He added a chat room and message board, along with "The Portal", where people could submit their own Flash creations. Newgrounds would grow to have portals for Games, Movies, Audio, and Art, and would spawn viral videos like the Numa Numa Dance. Google searches for "Newgrounds" peaked in December 2005.
In 2001, Robert Small and Tihan Presbie created the video hosting site Miniclip in London with £40,000 of their own funds. Their first video, about a dancing George W. Bush, became popular after they released an accompanying game. Miniclip would become the world's largest privately owned gaming site, and in 2008, the company was valued at £900 million. Google searches for "Miniclip" peaked in December 2007.
The overall popularity of Flash games has lessened in the 2010s, and Adobe has announced they would discontinue Flash in 2020. The original iPhone famously did not support Flash. In his Thoughts on Flash letter, Steve Jobs said "the mobile era is about low power devices, touch interfaces and open web standards - all areas where Flash falls short."Polygon writer Owen Good points to the popularity of mobile gaming as a contributing factor, saying that at the height of flash games' popularity in the mid-2000s, the only popular forms of mobile gaming were the Nintendo DS and PlayStation Portable. Large projects went underway to preserve and archive flash games after Adobe announced Flash would be discontinued, such as archiving games made by Nintendo.
Many Flash games in the late 1990s and early 2000s received attention through the use of shock comedy or real-world events, like McDonald's Videogame, a satire of McDonald's' business practices, or Darfur is Dying, about the War in Darfur, Sudan. Wired would write in 2017, "Flash games lent themselves to the exaggerated and cartoonish, a style that eventually evolved into an affection-at least amongst its best creators-for beautiful grotesquire. Like much of the younger gaming internet, Flash games defined boundaries simply to cross them; the best titles straddled a weird line between innocence and cruelty, full of gorgeous gore and enthralling body horror". One of the most controversial was Super Columbine Massacre RPG!, released on April 5, 2005, which reenacts the 1999 Columbine High School shootings in a Final Fantasy VI-like aesthetic.Betty Nguyen of CNN labeled the game as an example of a terrorist subculture, and the gunman in the 2006 Dawson College shooting admitted to playing the game on a website. Similarly, Tom Fulp created a game called Pico's School based after the Columbine shootings where the player must take down a goth school shooter. There are a few other controversies involving browser games and real-world events, such as the 2007 Virginia Tech shooting reenactment V-Tech Rampage, and NRA CEO Wayne LaPierre targeting the game Kindergarten Killers after the 2012 Sandy Hook shootings.
A persistent browser-based game is a video game that is both browser-based and persistent.
Persistent browser-based games usually rely on some kind of server-side code, although some games use technologies like Flash, ActiveX, and Java applets to store data on the client's computer. Games relying on client-side technology are rarer due to the security aspects that must be dealt with when reading and writing from a user's local file system - the web browser does not want web pages to be able to destroy the user's computer, and the game designer does not want the game files stored in an easily accessed place where the user can edit them. The server-side code will store persistent information about players and possibly the game world in some kind of database.
Sustainability, especially when combined with persistence, is a key distinction of a PBBG. This allows dynamic system modelling elements to develop and allow the game to progress even while the player is offline. Such games often last for several months.
Browser games can take advantage of different technologies in order to function.
Browser plug-ins were used to provide game technologies after being installed by the user. As of 2017 most companies (Oracle for Java plugin, Adobe for Flash Plugin) are considering ending support for their plugins. For example, Adobe Flash is expected to be removed from all browsers by the end of 2020. Also web browser manufacturers are leaving the idea of using plug-ins in their products in the future. Efforts have been made to preserve such games; for example, Flashpoint is a project aimed to preserve as many freely-available Flash-based games, with over 38,000 archived by January 2020.
|Windows||Mac OS X||Linux||License[notes 2]||Installed base[notes 3]|
|Java||Yes||Yes||Yes||Open source (free)||78%|
|Silverlight||Yes||Yes||Partial (Moonlight - LGPL)||Proprietary||62%|
|Unity Web Player||Yes - Also in Unity WebGL||Yes - Also in Unity WebGL||No- Works in Unity WebGL||Proprietary||1%|