> ## Documentation Index
> Fetch the complete documentation index at: https://docs.bibigpt.co/llms.txt
> Use this file to discover all available pages before exploring further.

# Free Online Subtitle Burner

> Burn SRT, VTT, or ASS subtitles permanently into your video right in the browser. No server upload, no watermark. Supports MP4, MKV, AVI, MOV.

## Overview

BibiGPT's Free Online Subtitle Burner uses ffmpeg.wasm to permanently hardcode SRT, VTT, or ASS subtitle files into your video — directly in the browser. Supports MP4, MKV, AVI, and MOV files. Customize font size, color, and position. No server upload, no watermark, no sign-up required.

## Pain Point

You need to share a video with burned-in subtitles for social platforms that don't support external subtitle tracks, or for viewers who watch without sound. Most tools either require paid software or upload your video to a remote server.

## Key Features

* Supports SRT, VTT, and ASS subtitle formats
* Hardcode subtitles into MP4, MKV, AVI, and MOV videos
* Customize font size, color, and vertical position
* Powered by ffmpeg.wasm — all processing in the browser
* No watermark, no sign-up, no server upload

## Highlights

Browser-local ffmpeg.wasm processing means even large video files stay private. ASS format support allows richly styled subtitles with custom fonts, colors, and positioning.

## Use Cases

* **Social Media Creators**: Burn captions into short-form videos for Instagram, TikTok, and YouTube Shorts where auto-captions are unreliable
* **Educators & Trainers**: Add permanent subtitles to instructional videos for accessibility
* **Localization**: Burn translated subtitles into videos for different regional audiences

## Tips

* For best visual quality, use ASS format with your preferred font settings
* Processing time scales with video length and resolution; shorter clips finish faster
* Preview the subtitle positioning before downloading to avoid re-processing

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**Related Feature**: [Free Subtitle Converter](https://bibigpt.co/features/free-online-subtitle-converter) — Try it now

**Upgrade to Pro**: Unlock unlimited usage → [View Pricing](https://bibigpt.co/pricing)

## Related Features

<CardGroup>
  <Card title="Free Subtitle Converter" href="/en/function-usage/platform-function/free-online-subtitle-converter" />

  <Card title="Free Video Trimmer" href="/en/function-usage/platform-function/free-online-video-trimmer" />

  <Card title="Free Video Speed Changer" href="/en/function-usage/platform-function/free-online-video-speed-changer" />
</CardGroup>