How to Convert Video, Audio, or Images with ffmpeg-web in Your Browser

Updated

ffmpeg-web is a browser-based UI for FFmpeg that runs entirely on your machine using ffmpeg.wasm, so you can convert media files without installing anything or uploading them to a server. To use it, open the site in a supported browser, load your file, pick an output format or options, run the conversion, and download the result. This works for typical video, audio, and image conversions, but very large files or exotic codecs may be slow or fail because everything runs in the browser's memory.

Before you start

  • A modern desktop browser. WebAssembly and the File System Access APIs behave best in current Chrome, Edge, or Firefox; mobile browsers are more likely to run out of memory.
  • Enough free RAM. The file is loaded into browser memory, so a 1 GB video can need well over 1 GB of working memory.
  • The source file on your local disk. Nothing is uploaded, which is the main privacy advantage of the browser version.

Step-by-step conversion

1. Open ffmpeg-web

Go to ffmpeg-web.netlify.app in your browser. The page loads the ffmpeg.wasm runtime, which can take a few seconds the first time. If the UI never becomes interactive, check that WebAssembly is enabled and that no extension is blocking large script downloads.

2. Load your media file

Use the file picker to select the video, audio, or image you want to convert. The file stays in your browser; it is not sent to a server. Expect a short delay while the file is read into memory — this scales with file size.

3. Choose the output format and options

Select the target container or format (for example MP4, WebM, MP3, WAV, PNG, JPG) and any options the UI exposes, such as codec, bitrate, or resolution. These map to FFmpeg arguments, so the same rules apply: changing the container without re-encoding may not be possible for every codec combination.

4. Run the conversion

Start the job and watch the progress indicator. Because ffmpeg.wasm runs single-threaded in most setups, encoding is noticeably slower than native FFmpeg — a clip that takes seconds on the command line can take minutes here.

5. Download the result

When the job finishes, download the output file to your disk. If the download never appears, the conversion likely ran out of memory; try a smaller file or a lower resolution.

Common problems and fixes

Symptom Likely cause What to try
Page loads but nothing happens ffmpeg.wasm failed to initialize Reload, disable script blockers, try another browser
Conversion stalls or crashes File too large for browser memory Use a smaller file, lower resolution, or the desktop version
Output won't play Container/codec mismatch Re-encode rather than just remuxing; pick a standard codec
Very slow encoding Single-threaded WASM Expect it, or switch to the native desktop build

When to use the browser version vs. the desktop version

Use the browser version when you want zero installation, are working with small-to-medium files, and care about files never leaving your machine. Use the native desktop version when you need speed, multi-threading, or are converting large or unusual files — it runs FFmpeg directly on your computer and avoids the browser's memory ceiling.