What's free
10,000 credits/month shared across Text-to-Speech, Speech-to-Text and more (~10 min TTS/month)
Rate limits
Concurrency tied to the Free plan (not numerically published)
The catch
The free tier is NON-COMMERCIAL only per the Terms of Use (a commercial license begins on paid Starter, $6/mo), and historically required attribution. API access is available on the free plan. No credit card to sign up.