burn subtitles into video api

If you want to burn subtitles into a video via an API, there are a few common ways to do it depending on your stack.

1) With FFmpeg in your own API

You upload:

• the video file
• the subtitle file (.srt, .vtt, etc.)

Then your backend runs FFmpeg to render subtitles into the video:

ffmpeg -i input.mp4 -vf "subtitles=subtitles.srt" -c:a copy output.mp4

Example API flow

• POST /burn-subtitles
• multipart upload with:
  • video
  • subtitles

Node.js example

import express from "express";
import multer from "multer";
import { execFile } from "child_process";
import path from "path";

const app = express();
const upload = multer({ dest: "uploads/" });

app.post("/burn-subtitles", upload.fields([
  { name: "video", maxCount: 1 },
  { name: "subtitles", maxCount: 1 }
]), (req, res) => {
  const video = req.files.video[0].path;
  const subs = req.files.subtitles[0].path;
  const output = `outputs/${Date.now()}.mp4`;

  execFile("ffmpeg", [
    "-i", video,
    "-vf", `subtitles=${subs}`,
    "-c:a", "copy",
    output
  ], (err) => {
    if (err) return res.status(500).json({ error: "FFmpeg failed" });
    res.json({ output });
  });
});

app.listen(3000);

2) Using a video processing API service

If you don’t want to run FFmpeg yourself, use a hosted video API. Popular options:

• Mux
• Cloudinary
• Shotstack
• Banuba (depending on use case)
• CloudConvert (for conversion workflows)

Example with Shotstack

You send a render job where subtitles are part of the timeline, and the service returns a rendered video.

3) If you only want subtitles as an overlay, not burned-in

Some services support:

• closed captions track
• selectable subtitles
• burned-in subtitles

Burned-in means the text becomes part of the video pixels, so it can’t be turned off.

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Important notes

• .srt must be properly formatted.
• If subtitle paths contain spaces or special characters, FFmpeg escaping matters.
• For better styling, you may want to convert subtitles to .ass and use advanced font styling.
• Burned subtitles are permanent, so keep an original unmodified video too.

If you want, I can give you:

1. a full Node.js/Express API
2. a Python/FastAPI version
3. a Cloudinary or Shotstack example
4. a Dockerized FFmpeg service