Compress PNG images
Cut PNG screenshots and graphics by 60–80% while keeping them sharp and transparent. It all runs on your device.
Drop your images here
JPG, PNG, WebP, AVIF, HEIC and GIF, up to 100 MB each
How it works
Compress in three steps
- 1
Drop your PNG images in.
- 2
Graviton reduces them to an optimized palette of up to 256 colors and recompresses them with OxiPNG.
- 3
Compare before and after, then download.
How PNG compression works
Most PNGs store millions of possible colors but only use a fraction of them. Graviton picks the best palette of up to 256 colors, adds subtle Floyd–Steinberg dithering so gradients stay smooth, then squeezes the file with OxiPNG.
Need it pixel-perfect?
Turn on "Lossless" under More options. Graviton then keeps every pixel and only optimizes how the PNG is stored. That saves less, but changes nothing.
Frequently asked questions
Is transparency kept?
Yes. Transparent and semi-transparent pixels are preserved in the optimized palette.
Are my images uploaded?
No. Graviton converts and compresses inside your browser, so your images never leave your device. Nothing is sent while you compress. When you download, the browser sends only a one-way fingerprint of the image, so the download can be counted and approved. Graviton stores none of it.
Why is a photo PNG still large?
Photos have smooth color changes that palettes handle less well. For photos, converting to JPG or WebP is usually far smaller.
Is it free?
Yes. Compressing and converting are free and unlimited, with no account needed. Downloading needs a free account, which includes 3 downloads a day with every format and setting. Pro removes the daily limit.