About Master Tools

Most quick file jobs — merge two PDFs, shrink a photo, pull a frame out of a video, count the words in an essay — end up costing you something out of proportion to the task. You install software, sign up for a trial, or hand a private document to a server you know nothing about, and get a watermark for your trouble.

Every one of those jobs is something a modern browser can already do on its own. So Master Tools does them there: you pick a file, the work happens on your machine, and you get the result back. No account, no queue, no upload.

When you choose a file, the browser hands the page a reference to the bytes already on your disk. The tool reads them with standard web APIs — canvas for images, WebCodecs and Web Audio for video and sound, WebAssembly where a format needs a real codec — and writes the result to a download. There is no endpoint on this site that accepts a file, so there is nothing for us to store, leak, or be asked to hand over.

The practical trade-off is honest: your device does the work. A 200-page PDF or a long video takes as long as your machine takes, and a phone is slower than a laptop. In exchange, the file stays yours.

The privacy page spells out exactly what is stored on your device and the two tools that fetch code from another server.

• PDF — Merge, split, compress, convert, and protect PDFs without uploading them.
• Image — Resize, compress, convert, and touch up images right in the browser.
• Video — Trim, compress, convert, and tweak video files on your own device.
• Audio — Cut, merge, convert, and adjust audio without a single upload.
• Text — Count, clean, transform, and generate text as you type.
• Developer — Format, validate, convert, and inspect the data you work with daily.
• Converter — Turn one file format into another, entirely on your device.
• Calculators — Quick, exact answers for money, health, dates, and units.

Favourites and recent downloads are kept in your browser so your daily tools stay one tap away. They are never sent anywhere, and clearing your browser data removes them.

Master Tools is built on other people's work. These are the libraries doing the heavy lifting, with the license each one is used under:

• @cantoo/pdf-lib (MIT) — reads, edits and writes PDF files
• pdfjs-dist (Apache-2.0) — renders PDF pages to pixels and pulls out text
• mediabunny (MPL-2.0) — reads and writes video and audio containers
• lamejs (LGPL-3.0) — encodes MP3 audio
• heic-to (LGPL-3.0) — decodes iPhone HEIC photos
• @jsquash/avif (Apache-2.0) — encodes AVIF images
• gifenc (MIT) — builds animated GIFs
• onnx-community/modnet-webnn (Apache-2.0) — separates a subject from its background
• qrcode / bwip-js (MIT) — draws QR codes and barcodes
• Next.js / React (MIT) — the site itself

Two of these are licensed under the LGPL-3.0: lamejs, which encodes MP3 audio, and heic-to, which decodes HEIC photos. Both are used as unmodified libraries, loaded separately from the rest of the site, so you remain free to replace either with your own build of the same library. A copy of each license travels with its package.

Neither was a casual choice. No browser exposes an MP3 encoder, and no permissively-licensed HEIC decoder exists at all — every one of them wraps the same LGPL library.