In video games with online gaming functionality, cross-platform play, also called cross-compatible play or cross-play, describes the ability of players using different video game hardware to play with each other simultaneously. It is commonly applied to the ability for players using a game on a specific video game console to play alongside a player on a different hardware platform such as another console or a computer. A related concept is cross-save, in which the player's progress in a game is stored in separate servers, and can be continued in the game but on a different hardware platform.

Cross-play is related to but distinct from the notions of cross-platform development, cross-platform releases, cross-buy, and cross-platform save game cloud synchronisation.

Cross-platform play, while technically feasible with today's computer hardware, generally is impeded by two factors. One factor is the difference in control schemes between personal computers and consoles, with the keyboard-and-mouse controls typically giving computer players an advantage that cannot be easily remedied. The second factor relates to the closed online services used on consoles that are designed to provide a safe and consistent environment for its players that require the businesses' cooperation to open up for cross-platform play. Up through September 2018, Sony Interactive Entertainment had restricted PlayStation 4 cross-platform play with other consoles, creating a rift between players of popular games like Rocket League and Fortnite Battle Royale. In September 2018, Sony changed their stance, and had opened up beta-testing for Fortnite cross-platform play. Sony officially stated it will allow any developers to support cross-platform play in October 2019.

Prior to the seventh generation of video game consoles, video games were typically developed for a single console with only a few games receiving cross-platform releases across multiple consoles. This was due to the unique processing architecture of each console, making development for each a closed ecosystem and requiring additional effort to port to other systems. With the seventh generation of consoles, which saw console systems use similar processor hardware as personal computers, cross-platform development for both consoles and personal computers became much easier to achieve using standard software libraries, game engines, and scripting languages that isolate platform-specific details from the specific elements for the game itself. Such tools enabled games to be released simultaneously for multiple platforms.

With the availability of the Internet, games have included online multiplayer components, allowing two or more users to play simultaneously on different computer systems. Games released for a platform may be able to take advantage of platform-specific networking libraries to accomplish this, such as the Winsock layer for Microsoft Windows. These games would not be able to be played cross-platform with other versions released on other systems. Instead, most games with online components and developed for multiple platforms generally use standard TCP/IP-type functions for communication between players' clients, or between a client and a game server, nullifying the intrinsic differences between hardware platforms.

There are some practical limitations for cross-platform play. In games where the player's computer or console acts as the server, the hardware capabilities may place limits on the number of players that that server can host, and thus preventing cross-platform play. Hardware also plays an issue in considering how much the player can customize the game on a computer to run at a high framerate, while console versions are fixed to run at the optimal experience on the set hardware configuration.

The most common limitation for supporting cross-platform play from a developer's stance is the difference in control schemes between consoles and computers. Computers with keyboard and mouse controls on personal computers are generally considered to have a significant advantage in games that require aiming, such as first-person shooters, over analog controllers for consoles. Console games are then subsequently developed with features such as aim assist to make up for the lack of precision controls. In 2010, Rahul Sood, the president of Voodoo PC, stated that Microsoft had terminated cross-platform play between Xbox 360 and computer players for an upcoming game claiming that even skilled console players "got destroyed every time" in matches against computer players of mediocre skill due to the difference between controller and keyboard-and-mouse controls, and thus would be seen as an embarrassment to the Xbox 360. Microsoft's Senior Director of Computer and Mobile Gaming Kevin Unangst countered this point, stating that Microsoft's internal testing found that much of the issues related to control scheme difference can be mitigated through a game's design and balance. Blizzard Entertainment implemented cross-platform play in its game Overwatch for all supported consoles and on personal computers, but due to the advantage keyboard-mouse players have over controllers, which greatly affects performance in the fast-paced game, they kept the game's competitive play mode segregated into console and computer player pools. Cliff Bleszinski believed that cross-platform play for his game LawBreakers was a "pipe dream", as he anticipated that by placing tools such as aim assist to help console players match computer players, computer players would be upset at the handicap this introduced, and the player base would react negatively towards this. Following wider adoption of cross-platform play in many mainstream titles starting around 2020, the issues of balancing the game with the use of aim assist in first-person shooters, where the game automatically locks onto targets for those using controllers, became of concern as a game with aggressive aim assist could lead to poor balance between cross-platform players.

Providing cross-platform play is seen as a means to keep a game's player base large even several months out after a game's release.