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). Success includes estimatedCredits (same number) so maxCredits is usable without doing the arithmetic. 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. An audio download miss is 502 audio_extract_failed with a split reason: blocked_rate (403/429, retryable, retryAfterSeconds=300), extract_timeout (retryable, 60s), extractor_unavailable (signed-URL / extractor miss, retryable, 120s), no_audio_format / restricted / live_unavailable (this video, retryable false). estimatedCreditsIfRetried is only present when retryable is true. A permanent miss with no captions sets obtainable:false and says no transcript is obtainable — it does not leave suggestedEndpoint:null as an open loop. Download budget is 20s (a doomed fetch used to sit for ~67s). blocked_rate opens a service-wide circuit (cacheScope=service, blockedRateConsecutive) so further downloads wait out the cooldown instead of deepening a YouTube block. When a published caption track exists, suggestedEndpoint=/v1/youtube/transcript — suggest, never substitute STT with captions. Response always includes source: "asr", asrProvider, languageIsDetected, numeric segments[{text,startMs,endMs}], text, durationSeconds, creditsUsed, estimatedCredits. Cache hits still bill — the cache is our margin.

What you get

• source:asr discriminator (pair with /transcript source:captions)
• estimatedCredits on success; maxCredits preflight without the arithmetic
• extractor_unavailable vs restricted / live / no_audio_format — retryable is per class
• Permanent no-captions miss closes the loop (obtainable:false)

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",
    "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 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