How this PNG compressor works
A PNG stores every pixel exactly, usually as 4 bytes (red, green, blue, alpha). That is why a screenshot or a logo export can weigh several megabytes. The trick that tools like TinyPNG and pngquant use is to convert the image to an indexed PNG: a palette of up to 256 colors, and one byte (or less) per pixel pointing into it. For screenshots, icons, diagrams and UI mockups, 256 well-chosen colors are visually identical to millions, and the file drops by 50 to 80 percent.
This tool does exactly that, in your browser. It picks the best 256 colors (or fewer, if you choose) with a quantizer, maps every pixel to its nearest palette color, keeps the alpha channel in the palette so transparency survives, and writes a new PNG with the browser's built-in deflate compression. Smaller palettes are packed into 4, 2 or 1 bits per pixel.
Lossy vs lossless, honestly
Smallest (256 colors) is the default and where the real savings are. It is technically lossy, but on most images you will not see the difference; compare the before and after previews to check. Photos with smooth gradients are the exception: they can show slight banding. For photos, a JPG is the better format anyway, and our PNG to JPG converter will usually cut them by 80 percent or more.
Lossless never changes a pixel. If the image already has 256 colors or fewer, it is rewritten as an exact indexed PNG, which can save a lot. Otherwise it is re-encoded with better row filtering than most apps use. Be aware that a browser cannot do the slow, exhaustive compression that desktop tools like OxiPNG or Zopfli do, so lossless savings on photo-like images are often small, sometimes zero. When the result is not smaller, the tool keeps your original file rather than handing you something heavier.
Why no upload matters
PNGs are typically screenshots, and screenshots are full of things you would rather not send to a stranger's server: chats, emails, invoices, dashboards, a password manager you forgot was open. This compressor runs entirely on your device. Load the page once and it works offline. It also means no file size cap and no daily limit.
Tips for the smallest PNGs
- Resize before compressing. A Retina screenshot is twice the width you need on most web pages. Halving the dimensions cuts the size to about a quarter before any compression.
- Try 128 or 64 colors for flat UI screenshots, charts and logos. The difference is often invisible and the file shrinks further.
- Use the right format. PNG for screenshots, text, logos and anything with transparency; JPG or WebP for photos. The short rule: if it has sharp edges or text, PNG; if it came out of a camera, JPG.
Want your screenshot on a background with rounded corners before you share it? The free screenshot beautifier does it in the browser too.