# caption.sh

> caption.sh is an API-first captioning service built for AI agents and automated video pipelines. Send a video with speech, get back the same MP4 with animated, word-timed captions burned in (the spoken word highlighted in sync, text auto-fitted to any aspect ratio). $0.10 per minute of video, prepaid. There is also a hosted MCP server so agents in Claude, Cursor and other MCP clients can caption videos directly.

Key facts:
- Output is a new MP4 with captions drawn on the frames. It is not a subtitle (SRT/VTT) file.
- Auth: a per-user API key (`sk_live_...`) from Dashboard > Keys, sent as `Authorization: Bearer <key>`.
- API base: https://api.caption.sh/v1 (async jobs: create, poll, download).
- MCP endpoint (hosted, streamable HTTP): https://mcp.caption.sh/mcp, same API key as a bearer token.
- Pricing: $0.10 per minute, rounded up to the next minute, billed from a prepaid balance. Credit packs: $5, $10, $20, $50 (+$5 bonus), $100 (+$10 bonus).
- Limits: videos up to 10 minutes. Results are kept for 24 hours.
- Every style option is optional; the simplest request produces a clean default.

## Docs

- [API reference (markdown)](https://caption.sh/docs.md): endpoints, auth, job lifecycle, every styling option, presets, errors, pricing
- [API reference (web)](https://caption.sh/docs)
- [Full context in one file](https://caption.sh/llms-full.txt): landing page, API reference, MCP tools and style recipes

## MCP

- [MCP server](https://caption.sh/llms-full.txt#mcp-server): tools `caption_video`, `get_caption_job`, `list_caption_styles`, `list_caption_jobs`, `get_caption_balance`, plus 9 ready-made style recipes

## Optional

- [Home page (markdown)](https://caption.sh/index.md)
- [Dashboard](https://caption.sh/dashboard): sign up, API keys, balance and billing

## Machine-readable API spec

- [OpenAPI 3.1 spec](https://api.caption.sh/openapi.json): full machine-readable API definition for agent tooling and codegen

## Free tools (no signup)

- [Tools hub](https://caption.sh/tools): free browser-based caption file utilities
- [SRT to VTT converter](https://caption.sh/tools/srt-to-vtt)
- [VTT to SRT converter](https://caption.sh/tools/vtt-to-srt)

## Blog
- [Blog](https://caption.sh/blog): guides on programmatic video captioning
- [AI captions API guide](https://caption.sh/blog/ai-captions-api): word-timed captions via one POST
- [Karaoke captions API](https://caption.sh/blog/karaoke-captions-api): active-word highlight styling via API
- [Video captioning API for Python](https://caption.sh/blog/video-captioning-api-python)
- [Captions.ai alternative](https://caption.sh/blog/captions-ai-alternative)
- [Zubtitle alternative for developers](https://caption.sh/blog/zubtitle-alternative)
- [Rev captioning API alternative](https://caption.sh/blog/rev-captioning-api-alternative)
- [Caption videos from an MCP server](https://caption.sh/blog/caption-videos-mcp-server)