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Language detection for transcripts

Audio language detection runs by default with language set to auto. For AI transcription, each segment reports its own language. Use these labels to work with mixed-language audio, or pass a language hint.

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  • language defaults to auto
  • A language on every segment
  • Pass any ISO 639-1 code as a hint

How it works

Automatic by default
With language set to auto, AI transcription identifies the language for you.
Per-segment languages
Each segment has its own language field, so mixed-language audio is labeled where it changes.
A dominant language
The transcription object reports the dominant language in language once it is known.
Hints when you know better
Pass a two-letter ISO 639-1 code such as en, de or es to steer AI transcription.
Caption language choice
For YouTube captions, language selects the caption track. With auto, transcript1 picks the video's original language.

Automatic

Use automatic language detection

Omit language or set it to auto. This is the default for every source.

Request body
{
  "platform": "youtube",
  "url": "https://www.youtube.com/watch?v=dQw4w9WgXcQ",
  "source": "stt",
  "language": "auto"
}

Per segment

Per-segment language for multilingual transcription

The top-level language is the dominant language. Each segment reports its own language, so you can see where the recording switches languages.

Response (shortened)
{
  "status": "completed",
  "transcript_source": "speech_to_text",
  "language": "en",
  "transcript": {
    "segments": [
      { "start": 0, "end": 3.4, "speaker": null, "language": "en", "text": "Good morning." },
      { "start": 3.4, "end": 7.9, "speaker": null, "language": "de", "text": "Guten Morgen." }
    ]
  }
}

Hint

Pass a language when you know it

Use a two-letter ISO 639-1 code. For a file upload, language is a form field.

cURL
curl -X POST "https://api.transcript1.com/v1/transcriptions?wait=60" \
  -H "Authorization: Bearer $TRANSCRIPT1_API_KEY" \
  -F [email protected] \
  -F language=de

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Frequently asked questions

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How do I set the language?

Send language in the request: auto, the default, or a two-letter ISO 639-1 code such as en, de or es.

Can I transcribe multiple languages in one recording?

Yes. With AI transcription each segment carries its own language, and the transcription reports the dominant one.

How does language work for YouTube captions?

It selects the caption track. With auto, transcript1 uses the video's original language. Auto-translated tracks are never used.

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