I downloaded a custom world that was just a .world file, not a sims3pack like usual, and put it in the InstalledWorlds folder in Documents but it isn't showing up in the game. Am I doing something wrong or is this particular world just not gonna show up?

For a world to work in the Installed Worlds folder, it has to be referenced in the DCCache (i.e, installed from a Sims3Pack).

Instead, put it in [Game Install Location] \Electronic Arts \The Sims 3 \GameData \Shared \NonPackaged \Worlds alongside SunsetValley.world, and it should work. Note- I've not tried this since Generations, perhaps someone with Gen could report if this still works.

Thanks, that worked I have Generations installed as well, so it definitely works with that.

Hihi, you saved us! Thank you too!

Just so you know, this post is STILL helping folks! Thank you!

I'm glad I'm still helping, thank you all for letting me know!

I'm so glad this thread is still active after all these years! GameData doesn't exist in my folder - any tips?

You're likely looking in the wrong place- look wherever your game is installed.

Thank you so much, I got it. But now I have a new problem, basically the exact same as this simmer, except it's Gruesim's Rosewood Park.

I assume this is a common issue, any pointers? I saw you replied to another simmer with a similar-ish issue. I tried your advice as well as what they did, i.e. housing the desired world's save file in another saved world's folder. But no luck

@Simbina As it's not directly related to this thread, the best thing to do is to start a new thread here, explaining the problem and what you have tried. Then other people will be able to help too.