If i speedrun a co-op game with my friends, can we all submit the same run? To we all enter the leaderboard?

If you speedrun a co-op game, only one of you should submit the run. There is a field on the submission page to add the usernames of the other runners. When approved, it will show on all of your profiles.

I've seen weird exceptions where there's just a variable stating whether the run was solo or otherwise but on principal @Pear and @Garsh are correct

To add to the above post by @Garsh, if a game doesn’t have a field for additional usernames and you think the leaderboard should support co-op runs, talk with the game moderators about it.

@RaggedDan That sounds like a very poor way to implement it; I would talk to the mods about that.

Thanks :)