AssemblyAI Speech-to-Text (Universal) vs Rev AI Speech-to-Text API

AssemblyAI Speech-to-Text (Universal)

OpenAPI 3.1 file with typed inputs and error responses on every operation. Two outages of an hour or more in the last 90 days, on 31 July and 16 September 2026.

Rev AI Speech-to-Text API

Reverb English at $0.20 an hour, foreign languages at $0.30. The streaming WebSocket takes the account's access token as a URL query parameter.

AssemblyAI Speech-to-Text (Universal)

1. Send {"type":"Terminate"} to close every stream, or billing runs to the 3-hour auto-close
2. Use speech_models (plural). The singular speech_model now returns 400 for current model names
3. Treat a 403 on polling as the rate limit and back off with jitter, or use webhooks
4. Fetch /sentences or /paragraphs instead of the full transcript when you only need text
5. Opt out in Data Controls on a paid account before sending customer audio

Rev AI Speech-to-Text API

1. Keep streaming URLs out of logs. They carry access_token
2. Send source_config: {"url": ...}, not media_url, even though the published SDKs still use media_url
3. Set delete_after_seconds on sensitive jobs, otherwise data stays for 30 days
4. Use notification_config webhooks rather than polling job status
5. Don't build on low_cost or fusion. Both are deprecated