Pokémon Prism is distributed only as a mod patch for existing copies of Pokémon Crystal.
Unlike regular patching systems, this patching system (which was developed by one of the original developers of Prism; more information available here) is complex enough to allow a full program to be encoded in a patch. Therefore, the patcher will detect which ROM you use as a patching base, warn a user if it is incorrect (helping both us and you from experiencing bugs from incorrect patching), and will allow you to generate both debug and release versions, as well as patch your savefile.
Likewise, you will be able to use the distributed patch to convert between the debug and release versions, so you don't need to keep both.
Please make sure you are using a modern browser. The patcher has been tested to work in both current versions of Chrome and Firefox.
Select the .bsp file containing the patch and the input file you want to patch, and hit 'Begin Patching'. Make sure to read the messages that the patcher will show. Keep in mind that all patching is done locally in your browser; nothing is sent to or from our servers, so this doesn't use up any data, nor does it require an internet connection.
If you are coming from a previous version of the ROM, make sure to also patch your existing savefile; they will not work without doing so. This also patches VC injected saved games (if extracted using a save manager), as well as the usual .sav, .dat, .bin, or a variety of other Gameboy save formats. These are usually named the same as your current ROM, in the same folder, and are extremely small in size.
We are not distributing the patch on this site at the current time. Please check existing sources to find it.
Every patch released contains a mixture of bug fixes, enhancements, content improvements, and more. Please visit the Changelogs page for details.