Compress PNG

How to compress PNG online

PNG is lossless, so re-saving one does little. The way to shrink a PNG substantially is to reduce how many colours it uses. A typical screenshot or graphic has thousands of subtly different shades that can be mapped to a palette of 256 colours with almost no visible change, and a palette PNG stores each pixel in one byte instead of four.

This is the same technique used by well-known PNG optimisers. The palette is built from the image itself, so the colours it keeps are the ones that matter, and full transparency including soft edges is preserved in the palette.

Photos with smooth gradients show some banding at 64 colours or fewer; screenshots, icons, diagrams and logos rarely do. For photographs, converting to JPG or WebP will save more than any PNG setting.

Start at 256 colours; most screenshots and graphics look identical and shrink by half or more. Drop to 128 or 64 only if you need a smaller file and can accept slight banding in gradients or shadows. Icons and simple logos often look perfect even at 32 colours, which gives the smallest files of all.

Compress PNG settings explained

When to compress a PNG

PNG compression is used by web designers, app developers and anyone publishing screenshots: documentation, tutorials, product images with transparent backgrounds and user interface assets. Smaller PNGs load faster and use less bandwidth, and for most graphics the palette version is indistinguishable from the original.

Before you compress

PNG compression works best on images with areas of flat colour, which is most screenshots, UI graphics, charts and logos. For photographs saved as PNG, converting to JPG or WebP will save far more than reducing colours, so use the image converter for those.

How to compress PNG, step by step

1. Press the Choose button or drag files onto the box. You can add several at once, and they never leave your device.
2. Set the number of colours to suit where the file is going. The defaults are a good starting point.
3. Press Compress. Images are processed in about a second each.
4. Check the result next to each file: the original size, the new size and the percentage saved. If the settings would make a file bigger, you are told instead of being given a larger file.
5. Press Download to save each compressed file.

What decides how small it gets

Two things decide how much an image shrinks: how many pixels it has and how much fine detail they hold. A 4000 pixel phone photo resized to 1920 pixels keeps less than a quarter of its pixels. After that, quality decides how much fine texture is kept. Photos of skies and walls compress more than photos of foliage, gravel or text, and graphics with flat colour compress most of all.

Is it safe to compress png online?

With most online tools, "online" means your file is uploaded to a company's server, processed there and kept for a while before it is deleted. Here it is not. The page downloads the converter code to your browser, and your file is read and processed inside the tab on your own device. It is never sent to TapToConvert or anyone else.

You can check this yourself: once the page and, for audio and video, the converter engine have loaded, turn off Wi-Fi and the tool still works. That also means there is no queue, no daily limit and no size cap set by a server. The only limit is the memory your browser gives a single tab.