Native captions with AI fallback
Retrieve captions from public YouTube videos or generate a transcript when captions are missing, using one API and one response contract.
Capslane
Capslane is a YouTube transcript API for extracting captions or generating transcripts, with timestamps, language selection, and production-ready controls for developers.
Overview
Capslane is a YouTube transcript API that retrieves captions from public videos and generates transcripts when captions are unavailable. It is built for developers who need a single endpoint for caption extraction, generated fallback, and timestamped output.
The API returns a stable response contract across native, generated and cached results. Documentation and pricing pages show support for server-side API keys, asynchronous jobs, shared caching, monthly usage limits, and usage tracking tools for production workflows.
Key capabilities
Flexible output formats
Return either plain text or timestamped segments. The docs also note support for structured JSON output and a text mode.
Language selection
Choose a preferred ISO language code for extraction. If the exact track is unavailable, the API falls back to the first available transcript and reports other languages.
Async job workflow
Handle longer videos with asynchronous jobs. The API can return a job ID and a separate job endpoint reports status until completion.
Stable cached responses
Reuse results through a shared transcript cache. Cached, native and generated responses keep the same structure, which simplifies downstream processing.
Production controls
Use workspace API keys, request history, monthly usage limits and request logs in higher plans to manage production usage.
Common use cases
Video apps with fallback transcript handling
Build a transcript feature for a video app that first tries native captions and falls back to generated text when captions are missing, without changing the response shape your code consumes.
Search and analysis pipelines
Index transcript text for search, analysis or retrieval workflows that need timestamped segments and consistent language metadata.
Long-running transcript jobs
Process longer videos with an asynchronous request flow, polling job status until a transcript is ready instead of blocking the initial request.
Team API operations
Manage production usage for a team or product by keeping keys server-side, tracking monthly limits and reviewing request history or logs on higher plans.
Pros and Cons
Pros
- Combines native caption retrieval and generated fallback in one API.
- Keeps native, generated and cached responses in the same format.
- Supports timestamped segments, plain text output and language selection.
- Includes server-side keys, workspace quotas and usage tracking for production use.
- Offers a free tier and higher-volume paid plans for teams with growing usage.
Cons
- The documentation says generated transcripts may require polling a job endpoint, so some requests are not immediate.
- The reliability pages note that YouTube availability varies by region, account state and upstream changes, so coverage is not guaranteed for every video.
FAQ
How do I authenticate requests?
Capslane sends the request to its transcript API using the workspace API key in the x-api-key header. The docs say to create a server key in the dashboard and keep it server-side.
Can I request a specific transcript language?
Yes. The API accepts a preferred ISO language code. If that track is unavailable, Capslane returns the first available transcript and lists the available languages.
What happens if a video has no captions?
When no captions are available and the mode allows generation, Capslane starts an asynchronous job and returns a job ID. You then poll the job endpoint until the transcript is completed or failed.
Do cached transcripts return a different response format?
Yes. Native, generated and cached transcripts use the same response structure, and the cached field indicates when no extraction was needed.
Is there a free tier?
The pricing page says Capslane offers a free plan with 50 requests per month, plus paid plans for higher monthly request volumes. Usage resets monthly, including on annual subscriptions.
Quick Facts
- Category
- Developer Tool
- Primary use
- YouTube caption extraction and transcript generation
- Platform
- Web API
- Auth
- Workspace API key in x-api-key header
- Source domain
- capslane.com
- Pricing
- Free tier plus paid plans
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