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Subtitle API

Subtitle API that transcribes and burns in subtitles automatically.

Turn spoken audio into hardcoded subtitles from your backend: no SRT handling, no ffmpeg scripts, no manual timing.

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Quick answer

A subtitle API generates subtitles from a video's speech and returns them in a usable form. The AnimateCaptions subtitle API transcribes the audio automatically (the spoken language is auto-detected), times every word, and burns styled subtitles directly into the video, returning a finished MP4. Create a job with POST /api/v1/jobs, poll GET /api/v1/jobs/{id}, then download the result.

Key takeaways

  • Automatic speech-to-text with word-level timestamps and automatic language detection.
  • Subtitles are burned into the video (open captions), so they show on every platform and player.
  • Choose sentence-style subtitles or punchy word-by-word captions from 37 presets.
  • Works from any language that can make HTTPS requests; no SDK required.

Automatic transcription with word-level timing

Every job starts with speech recognition that returns a timestamp for each word. Those timings drive when each subtitle chunk appears and which word is highlighted, so subtitles stay in sync without manual timing work.

Burned-in subtitles instead of sidecar files

Instead of returning an SRT or VTT file you then have to attach or render yourself, the API renders the subtitles into the video frames. The output MP4 plays with subtitles everywhere, including platforms that ignore or strip subtitle tracks.

Languages

The spoken language is detected automatically from the audio, so the same request works for English, Spanish, Portuguese, Hindi, Arabic and the other supported languages without any extra parameter.

Traditional subtitles or animated captions

Pick a sentence-level style for classic subtitles, or a short-chunk animated style for TikTok, Reels and Shorts. Every style accepts the same customization options for font size, colours, stroke, background and position.

Burned-in subtitles vs sidecar subtitle files

FeatureBurned-in (this API)Sidecar SRT/VTT
Visible on social platformsAlwaysDepends on the platform
Viewer can turn offNoUsually yes
Animated stylesYes, 37 presetsNo, plain text
Extra rendering stepNone, MP4 returnedYou render or attach it
Step by step

From API request to subtitled MP4.

  1. 1

    Create a free API key

    Sign in at animatecaptions.com/developers and create a personal API key (ac_live_…). Send it as an Authorization: Bearer header on every request.

  2. 2

    Create a caption job

    POST /api/v1/jobs with a source_url (a public direct link to an MP4 or MOV) or with filename + file_size to receive a presigned upload URL. Add style, position and optional customization.

  3. 3

    Poll the job status

    GET /api/v1/jobs/{id} moves through queued, transcribing and rendering to completed. A short clip usually finishes in one to two minutes.

  4. 4

    Download the captioned MP4

    Completed jobs include a one-hour download_url, or call GET /api/v1/jobs/{id}/download. The job also appears in your project list for manual tweaks.

Editor walkthrough

Edit and preview before you export.

Correct words, customize the style, reposition individual lines, and preview the burned-in result.

Related guides

Continue with a specific workflow.

API & MCP docsCaption APIHardcode subtitles into a video
Common questions

Frequently asked questions.

Does the subtitle API translate subtitles?

It subtitles the language that is spoken in the video. Translation is not part of the API today.

Can I get the transcript text as well?

The transcript is editable in the web editor for every API job. The API itself returns the captioned MP4.

How much does the API cost?

API keys are free. Jobs count against your plan's monthly uploads: the free plan includes 3 videos per month up to 2 minutes with a watermark; paid plans remove the watermark and raise the limits.

Which video formats are supported?

MP4 and MOV, up to 500 MB on the free plan and 2 GB on paid plans, sent as a public direct link or uploaded to a presigned URL.

Where are the full API docs?

At animatecaptions.com/developers, which also lists every caption style (GET /api/v1/styles needs no key) and the MCP setup for AI agents.

Add accurate animated captions to your next clip.

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