RAR support happened!
Status update! RAR is now supported as of 18.5.0, see release notes.
We switched from 7-zip (the tool) to unarchiver, which contains a from-scratch implementation of .rar, which mean it doesn't suffer from the unRAR restriction.
RAR policy
Some games on itch.io use the RAR archive format.
However, itch (the desktop app) does not support RAR and will never support it.
The main reason is its license, which prevents us from shipping a RAR decompressor.
Players: if a game you like is using .rar, get in touch with the developer and tell them about this page.
Developers: use .zip if you want everybody to be able to open it, use .7z if you want small downloads.
More information:
Making your software itch-compatible (a general guide)A good comparison between 7z and rarThe 7-zip license (see the 'unRAR restriction')
FAQ
Do you seriously expect RAR to go away?
Well, we can try! The nice thing with software is that you can sincerely wish for its extinction without remorse.
I've run some tests and RAR is smaller/faster/better/stronger
That doesn't solve the licensing problem, so it's kind of a moot point.
But isn't the licensing thing only for RAR compressors, not decompressors?
Maybe, but the rar-free version of 7-zip is available in most linux distributions without having to enable non-free repos, and that makes our lives a lot easier.
Can I fork itch & add RAR support?
Hey, it's open-source, do as you want! But 1) if you're going to touch itch code, I implore you to pick a more useful problem to tackle instead: https://github.com/itchio/itch/issues/ 2) we won't merge it in the main version.