Freesound

Freesound is a collaborative database of sounds run by the Music Technology Group at Universitat Pompeu Fabra in Barcelona. Members upload field recordings, foley, ambiences, instrument samples and odd one-off noises, and anyone can search and download them with a free account.

It is not an AI generator. It earns a place here because creators pair it with AI tools: generate a sound you cannot find, find a real recording you cannot generate. The thing to check is the license on each sound. Some are public domain, some need attribution, and some forbid commercial use, and the license is shown on every sound page. Note the author and license for each file you use, and credit them where the license asks you to.