This tool allows you to check any text against the word filter of SIFAS. Filtered words will be marked red.
While this checker is based on the SIFAS GL pool, it should also be usable for SIF as the word filter is very similar. However, most of the block list does not apply to the JP version.
The bad word list is not guaranteed to be complete. Currently, only all possible words up to five characters are bruteforced (the previous checker went up to six), and while I tested the game against some profanity lists I found online, there might still be a lot missing. If you have a message that gets blocked in the game but looks fine here, let me know and I'll find out what's wrong: @Suyo_ on Twitter or Suyooo#7026 on the SIF Discord or the r/LL Discord.
The raw list of blocked words is available too, but obviously, a content warning: there's all kinds of slurs and offensive words in various languages. You can find the bad word list here. (Chrome and it's derivatives just show it raw and ugly, use Firefox instead (that's advice in general too))