AssemblyAI · Transcription model

Universal-3.5 Pro

assemblyai/universal-3-5-pro

Transcription

Released Sep 22, 2026

Universal-3.5 Pro is AssemblyAI's speech-to-text model served through its Sync API, returning a complete transcript with word-level timestamps in a single synchronous response for audio clips up to 120 seconds....

Specifications

Input: wav, mp3, flac, m4a, ogg, webm, aac, opus · base64 JSON, multipart file or URL · up to 25 MB
Output: text; verbose_json adds language, duration, segments and word timestamps
Billing: per second of audio

Use it

POST /api/v1/audio/transcriptions · MCP transcribe · full reference

curl https://omnirail.org/api/v1/audio/transcriptions \
  -H "Authorization: Bearer $OMNIRAIL_KEY" \
  -F model=assemblyai/universal-3-5-pro \
  -F file=@meeting.mp3