YouTube Audio Transcript API

What is the YouTube Audio Transcript API?

Transcribes YouTube audio with Whisper-class ASR when the video has no published captions (or when you want speech-to-text regardless). Separate from /transcript — that endpoint only returns YouTube's caption tracks. Pricing is duration-based and honest: creditsUsed = ceil(durationSeconds / 60) × 2 (badge: 2 credits/min of audio). Pass maxCredits to refuse expensive jobs before any STT runs (400 cost_exceeds_max, 0 credits). Prefers Groq whisper-large-v3-turbo when GROQ_API_KEY is set (measured: ~20 min ≈ 12s e2e, ~82 min ≈ 49s); otherwise OpenAI whisper-1. Audio is re-encoded to 16 kHz mono 32 kbps before upload so podcast-length jobs stay under the ~25 MB ceiling. Sync path is capped at 90 minutes under Cloudflare's 110s hard deadline; longer videos return 400 duration_too_long with estimatedCredits before any STT spend. Response always includes source: "asr", asrProvider, languageIsDetected, numeric segments[{text,startMs,endMs}], text, durationSeconds, creditsUsed. Cache hits still bill — the cache is our margin.

What you get

• source:asr discriminator (pair with /transcript source:captions)
• Per-minute pricing + maxCredits preflight
• Uniform segments[] with numeric startMs/endMs (verbose_json)
• Groq-first path; 90-minute sync cap from measured e2e

Platform limits

Honest ceilings from the upstream platform surface — not Captapi bugs. Unexpected truncation here is usually the platform, not us.

• Sync transcription is capped at 90 minutes (Cloudflare ~110s hard deadline + ~25 MB upload). Longer videos — including multi-hour livestreams — return 400 duration_too_long with estimatedCredits (0 credits, no STT).
• Audio is speech-reencoded (16 kHz mono 32 kbps) before ASR; rare extract failures may still hit audio_too_large.
• Requires GROQ_API_KEY in production for the 90-minute band; without it the OpenAI fallback is far slower and should stay on a tighter operational cap.

Fill in the parameters below and copy a ready-to-run request, or open the live Playground to run it against your account (no API key paste).

curl "https://api.captapi.com/v1/youtube/audio-transcript?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DjNQXAC9IVRw" \
  -H "Authorization: Bearer capt_live_..."
# or: -H "x-api-key: capt_live_..."

Example response

{
  "success": true,
  "data": {
    "platform": "youtube",
    "videoId": "jNQXAC9IVRw",
    "url": "https://www.youtube.com/watch?v=jNQXAC9IVRw",
    "source": "asr",
    "asrProvider": "groq-whisper-large-v3-turbo",
    "language": "en",
    "languageIsDetected": true,
    "durationSeconds": 19,
    "segments": [
      {
        "text": "Alright, so here we are in front of the elephants.",
        "startMs": 0,
        "endMs": 4000
      },
      {
        "text": "The cool thing about these guys is that they have really, really, really long fronts.",
        "startMs": 4000,
        "endMs": 12000
      },
      {
        "text": "And that's cool.",
        "startMs": 12000,
        "endMs": 14000
      },
      {
        "text": "And that's pretty much all there is to say.",
        "startMs": 16000,
        "endMs": 19000
      }
    ],
    "text": "Alright, so here we are in front of the elephants. The cool thing about these guys is that they have really, really, really long fronts. And that's cool. And that's pretty much all there is to say.",
    "creditsUsed": 2
  }
}

Billing metadata is returned in response headers: X-Captapi-Credits (credits charged), X-Captapi-Cache (hit or miss), and X-Captapi-Source. Failed requests (4xx/5xx) are never charged. See the full list of error codes in the error reference.

Response structure

A successful call returns success, cached, creditsUsed, and a data object with the following fields:

Parameters

Authentication: send your key as Authorization: Bearer capt_live_.... A typical call costs 2 credits/min of audio. Pass cache=true for a free 24h cache hit; default is always fresh.

How it works

1. 1. Sign up — get 100 free credits, no card required.
2. 2. Create a key from your dashboard.
3. 3. Send one request to /v1/youtube/audio-transcript and parse the JSON response.

Use cases

Frequently asked questions

More YouTube APIs