I don’t think the game is inappropriate. It’s the CHAT that makes it 13+. I joined TFM because I saw wisteriamoon play it and it looked fun. Lmao so basically I joined transformice when I was 10. I am 12 now. I joined because I thought it was kid friendly xd. But now I’m used to the swearing. If the kids keep the language filter on, or just click whisper (tab) on someone’s username to cover the chat, I think it’s probably okay to be 10+, or somewhere around there.
Edit: Plus, if someone says something inappropriate, SOMETIMES a mod will give a warning saying “please be more appropriate for all ages”, so.

8-13 from

this game is just fun ill prob be playing it with my kids, i like social games because i dont get to talk to people much and this game is just nice

It's for people who want their freedoms of speech curtailed.

There's no chat filter and that's something I enjoy about this game. It only (optionally) blocks out heavy slurs like nigg or f*g. So if you're young, you don't have to be surrounded by that, while edgy people have something to be edgy on. Heavy filtering is what kills social platforms, like what happened to Roblox and Animal Jam. The whole aesthetic of the game is cutesy and innocent french rats getting cheese. So I'd say 10-13+

13+ is good for me