Building a Browser-Based Video Editor with FFmpeg WASM

July 9, 2025

I've always been fascinated by the idea of bringing powerful desktop applications to the web. That's why I decided to build a browser-based video editor using FFmpeg and WebAssembly. The result is Browser Video Editor, a tool that lets you edit videos entirely in your browser without uploading anything to a server.

Browser Video Editor Interface The Browser Video Editor interface with a simple drag-and-drop area for uploading videos

Why Build This?

We've all been there - you need to quickly trim a video, convert it to a different format, or extract audio, and you have to either:

  • Download and install heavy desktop software
  • Upload your video to an online service (privacy concerns!)
  • Use command-line FFmpeg (not beginner-friendly)

I wanted to create something that combines the power of FFmpeg with the convenience of a web browser, all while keeping your videos private by processing everything locally.

The Technical Challenge

The biggest challenge was getting FFmpeg to run in the browser. FFmpeg is a powerful command-line tool written in C, and browsers can only run JavaScript. This is where WebAssembly (WASM) comes in - it allows us to compile C code to run in the browser at near-native speeds.

I used ffmpeg.wasm, which is a pure WebAssembly / JavaScript port of FFmpeg. This means:

  • No server uploads needed - everything runs in your browser
  • Your videos stay private
  • No installation required
  • Works on any modern browser

Key Features

The tool currently supports essential video editing operations:

Video Processing:

  • Trim videos by specifying start and end times
  • Convert between formats (MP4, WebM, AVI, MOV, and more)
  • Compress videos by adjusting quality settings
  • Extract frames as images

Audio Operations:

  • Extract audio from videos
  • Remove audio tracks
  • Convert audio formats

Advanced Features:

  • Adjust video resolution
  • Change frame rates
  • Apply video filters
  • Merge multiple videos

The User Experience

I focused on making the interface as simple as possible:

  1. Drag and drop your video (or click to browse)
  2. Choose your editing operation
  3. Adjust settings if needed
  4. Click process and download the result

No accounts, no uploads, no waiting for server processing. Everything happens instantly in your browser.

Technical Implementation

Here's a simplified overview of how it works:

// Load FFmpeg WASM
const ffmpeg = createFFmpeg({ log: true });
await ffmpeg.load();

// Write input file to FFmpeg's virtual file system
ffmpeg.FS('writeFile', 'input.mp4', await fetchFile(videoFile));

// Run FFmpeg command
await ffmpeg.run('-i', 'input.mp4', '-t', '10', 'output.mp4');

// Read the output file
const data = ffmpeg.FS('readFile', 'output.mp4');

// Create download link
const url = URL.createObjectURL(new Blob([data.buffer]));

The beauty of this approach is that FFmpeg's virtual file system runs entirely in the browser's memory. No data leaves your device.

Challenges and Solutions

Memory Management: Large video files can consume significant browser memory. I implemented:

  • File size warnings
  • Chunked processing for large files
  • Automatic memory cleanup after processing

Performance: WebAssembly is fast, but not as fast as native FFmpeg. To improve UX:

  • Added progress indicators
  • Implemented web workers to prevent UI freezing
  • Optimized FFmpeg commands for browser environment

Browser Compatibility: Different browsers have different WASM capabilities. The tool:

  • Detects browser capabilities on load
  • Falls back gracefully for unsupported features
  • Shows clear error messages when needed

What's Next?

I'm excited about adding more features:

  • Real-time video preview
  • Batch processing multiple files
  • More video filters and effects
  • Simple video timeline editor
  • Preset templates for common operations

Try It Yourself

The tool is completely free and open to use at ffmpeg.abhikhatri.com. Whether you need to quickly trim a video for social media, convert a file for compatibility, or extract audio from a presentation, it's all just a few clicks away.

Conclusion

Building this tool taught me a lot about WebAssembly, FFmpeg, and the current state of web technologies. It's amazing that we can now run complex video processing entirely in a browser. As browsers continue to evolve and WebAssembly becomes more powerful, I'm excited to see what other desktop-class applications we can bring to the web.

Give it a try and let me know what you think! Your feedback will help shape the future development of this tool.