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POST
Transcribe a short audio file

Authorizations

Authorization
string
header
required

Your AssemblyAI API key. Optionally prefixed with Bearer. Also accepted as the token query parameter.

Headers

X-AAI-Model
enum<string>
required

Model identifier used for request routing. The canonical value is universal-3-5-pro; u3-sync-pro and u3-pro are accepted as legacy aliases.

Available options:
universal-3-5-pro

Query Parameters

token
string

API key alternative for clients that cannot set the Authorization header. The header wins when both are present.

Body

multipart/form-data
audio
file
required

Raw audio bytes. Set the part's Content-Type to audio/wav for WAV files or audio/pcm for raw S16LE little-endian PCM.

config
object

Optional transcription configuration.

Response

Transcription completed successfully.

text
string
required

Full transcript of the audio.

words
object[]
required

Per-word confidence scores, plus start/end timestamps when the request sets timestamps to true.

confidence
number<float>
required

Overall transcript confidence (0–1).

audio_duration_ms
integer
required

Duration of the submitted audio in milliseconds.

session_id
string<uuid>
required

Server-generated request identifier. Include this in support requests.

request_time_ms
number<float>

End-to-end server-side processing time for the request in milliseconds, covering queue wait, decoding, and inference.