About – Free Image Compressor

Most “compress my image” websites work the same way: you upload your photo to somebody else’s computer, wait while it is processed on their server, and then download the result. That is a reasonable design for a photo-sharing service. It is a poor fit for a document, a passport photo, a client deliverable or anything else you would rather not hand to a stranger’s server.

This tool takes the opposite approach. The compression runs on your own device, in your own browser, and your images are never uploaded. That is not a policy promise — it is simply how the code works. There is no upload endpoint to opt out of.

Why it is free

There is no server doing the work, so there is no per-image cost to pass on. The site is a handful of static files served from GitHub Pages, which is free hosting. That is the entire business model.

How it actually works

Your browser already knows how to read images and how to write them back out — that is what the File API, createImageBitmap() and the Canvas API are for. This site uses those built-in capabilities and adds two things of its own:

A real PNG compressor. A PNG quality slider does not exist, so this tool shrinks PNG files the way that actually works: it builds a colour palette with median-cut quantisation, refines it, optionally dithers the result, and writes the image out as an indexed-colour PNG with adaptive scanline filtering. Transparent images keep their transparency. Greyscale images that fit a 1, 2 or 4 bit depth are stored losslessly at that depth.
A size search. If you give it a target file size, it binary-searches for the highest quality that still fits, rather than guessing. It stops before the picture becomes unusable and tells you when the target could not be reached.

Large images are processed in a Web Worker, so the page keeps responding while a big file is being worked on. If your browser cannot run a worker, the same code runs on the main page instead.

What it deliberately does not do

No accounts, no sign-in, no email required.
No watermark and no cap on how many images you compress.
No analytics or advertising scripts are loaded in this version.
No automatic resizing. Dimensions change only if you ask for it.
No pretending a PNG quality slider means the same thing as a JPG one.

Advertising

The tool is currently ad-free. Advertising may be introduced later to help cover hosting, but any ads will be clearly marked and kept away from upload and download controls. This page and the Privacy Policy will be updated before ads are enabled. Your file choices, filenames and image contents will never be shared with an advertising system.

Open source

The whole site is plain HTML, CSS and JavaScript with no build step and no third-party libraries. You can read every line that runs on your machine, and if you prefer, you can run a copy yourself.

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