The co-op Half-Life mod, without installing anything
Sven Co-op is Half-Life turned co-operative: instead of shooting each other, a group of players works through a map together against the game's monsters and soldiers. Playing it normally means installing a standalone client and finding a server with room. This page is about the other way — opening a map in a browser tab and sending your friends a link.
Host a Sven Co-op map nowBrowse every co-op mapIt is a co-operative modification of Half-Life. The same weapons, the same monsters and much of the same world, rebuilt so that a team plays through it together. Some maps are the original Half-Life campaign adapted for a group; most are original community creations built specifically for co-op, and they range from short arena maps to long multi-part campaigns.
It has been developed by the Sven Co-op team since the late 1990s, and it is free: you do not need to own Half-Life to play it. That is the reason it still has an active map-making community decades later.
The usual route is to install the standalone client, wait for it to download, launch it and browse a server list. That works, and if you are on your own machine with time and disk space it is the fullest version of the game.
It stops working when you are on a laptop you do not administer, a Chromebook, a machine at school or work, or someone else's computer. Anywhere you cannot install software, the download is the whole obstacle. It also stops working when you just want to show someone a map now rather than talk them through a download.
The engine that runs Sven Co-op has been compiled to WebAssembly, which means it runs inside the browser tab itself rather than on a server somewhere streaming video to you. There is nothing to install and no account to make.
Pick a map, press Host, and the map loads. Maps that are already stored here start immediately; the rest are fetched at the moment you press the button, then start. From there it is the game — same weapons, same monsters, same maps.
Hosting gives you a link. Anyone you send it to opens it and is in your game. They do not install anything either, and neither of you has to configure a router, forward a port or rent a dedicated server.
That is usually the part that kills a spontaneous co-op session. One person has the game, the other does not, and the setup takes longer than the map. A link removes that step for everyone.
If you have never played it, start with something short and rated well rather than a multi-hour campaign. The map index here lists every map with its author, its difficulty as the author rated it, and its community rating where players have actually voted.
Maps are tagged easy, medium or hard, and the easy ones are genuinely a reasonable first hour. Longer campaigns are split across several map files and are worth saving until you have a group who want an evening of it.
Nothing. Sven Co-op itself is free, and playing it here is free. There is no account, no signup, and no download step to pay for in time or disk space.