About WebUtil
WebUtil is a free set of file conversion tools that run entirely in your browser. Files are converted on your own device and never uploaded to a server.
How the conversion works
Images are decoded and re-encoded with the image codecs built into your browser. HEIC photos use libheif when the browser cannot read HEIC itself, and PNG compression uses UPNG.js.
Video and audio tools run FFmpeg compiled to WebAssembly (ffmpeg.wasm). The engine, about 30 MB, is downloaded once from a public CDN the first time you use a video tool; your files stay on your device.
PDF tools use pdf-lib to build and optimize PDFs and Mozilla's pdf.js to render PDF pages as images.
Limits
Each file can be up to 100 MB for images, 500 MB for video and audio, and 200 MB for PDFs, with up to 5 files per batch. Large videos convert more slowly because WebAssembly runs on a single thread.
Who runs this site
WebUtil is an independent project funded by ads. It never sees, stores or sells your files.
Last updated 2026-10-10.