What video formats are supported?

MP4, MOV, and WebM are supported for input. Output is always MP4 (H.264/AAC).

How long does it take to process?

Approximately 1–5× the video duration depending on your device. A 5-minute video typically takes 5–25 minutes. Processing happens entirely on your device — a more powerful CPU means faster results.

Is my video uploaded to a server?

No. FFmpeg runs entirely in your browser via WebAssembly. Your video never leaves your device.

Can I change the subtitle font or colour?

Yes. You can customise font family, size, colour, outline, and vertical position before processing.

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🎬

🌐 Runs in Browser⏱ Est. 1–5× video durationNEW

Video Caption Burner

Name: Video Caption Burner
Author: Zeraku

Burn SRT subtitles into video files directly in your browser

Try It Now — Free

What is Video Caption Burner?

Combine a video file and an SRT subtitle file in your browser to produce a captioned video with subtitles permanently embedded. Powered by FFmpeg.wasm — no server required, no quality loss from re-uploading. Customise font, size, and position before export.

Key Features

Permanently burn SRT subtitles into MP4, MOV, WebM

Customise subtitle font, size, colour, and position

Live preview before processing

FFmpeg.wasm — no server, no quality loss from re-encoding

Supports videos up to 500 MB

100% browser-based — video never leaves your device

Direct import from Zeraku Subtitle Converter or Audio Transcription

How It Works

Upload Files

Upload your video file (MP4, MOV, WebM) and your SRT subtitle file. Or import the SRT from the Subtitle Converter or Audio Transcription tool.

Customise

Adjust font family, size, colour, and vertical position. Preview on a frame of your choice.

Process

FFmpeg.wasm renders the video with embedded subtitles in a Web Worker. Progress is shown in real-time.

Download

Download the final MP4 with subtitles permanently burned in, ready for sharing on social media or archiving.

Who Is This For?

▸Content creators adding permanent captions to YouTube Shorts or TikToks
▸Educators creating accessible lecture videos with subtitles
▸Marketers producing captioned social media videos for silent viewing
▸Translators delivering localised videos with subtitles burned in
▸Archivists preserving historical footage with permanent captions

Why Use Video Caption Burner?

Most subtitle burning tools require uploading your video to a cloud server — slow, expensive for large files, and a privacy risk for personal or sensitive videos. Zeraku's Video Caption Burner runs FFmpeg entirely in your browser using WebAssembly. Your video never leaves your device. No file size tiers, no subscription, no watermark. For creators who regularly produce captioned content, this is the fastest zero-cost workflow available.

Beginner's Guide

"Burning in" subtitles means the subtitle text is permanently embedded into the video image itself — unlike "soft" subtitles which are stored separately and can be turned off. Hard-coded subtitles are visible on any device or platform, including Instagram, TikTok, and offline players that do not support external subtitle files. To use this tool: upload your video and an SRT subtitle file (you can create one using Zeraku's Audio Transcription tool), customise the appearance, and download the final video.

Technical Details

Powered by @ffmpeg/ffmpeg running in a SharedArrayBuffer-enabled Web Worker. The video and SRT files are written to FFmpeg's in-memory virtual filesystem (MEMFS). A subtitle filter chain (subtitles=sub.srt:force_style=...) is applied via libass for hardware-accelerated text rendering. Output is encoded as H.264/AAC MP4 using the libx264 codec. Processing speed is approximately 0.3–1× real-time depending on device GPU acceleration support. SharedArrayBuffer requires COOP/COEP headers which are set in next.config.ts.