Compress images

How to compress an image

1. Drop one or more JPG, PNG, WebP or AVIF files onto the box above, or paste a screenshot.
2. Drag the size slider to the file size you want, or type an exact limit in KB. Under the slider you see an instant estimate of what it will take, such as the quality level or whether the image has to be scaled down. Prefer to pick the quality yourself? Choose Set quality instead.
3. Press Compress. The tool searches for the highest quality that fits your size. With a single image the result refreshes a moment after you change a setting, and the comparison slider lets you drag between the original and the compressed version.
4. Optionally pick a different Output format. WebP and AVIF are usually the smallest choices for photos on the web.
5. Download the file, or take a batch as one ZIP.

The size of every file is shown before and after, together with the percentage saved. If a file cannot be made smaller, you get the original back instead of a bigger one.

What happens to your pictures

Compression runs entirely in your browser. Your images are decoded, re-encoded and handed back to you by WebAssembly code in a background worker, so nothing is uploaded and the page stays responsive even with large photos. Because the decoding is done by WebAssembly rather than your browser’s canvas, very large pictures also work on phones where canvas limits would otherwise cut them off.

Choosing quality and format

JPG uses the MozJPEG encoder, which produces files noticeably smaller than most camera and phone software at the same visual quality. Values between 70 and 85 are right for most photos; below 60 you may start to see blocky areas and ringing around edges.

PNG is lossless, so at quality 100 the tool only optimises how the data is stored. Lower values reduce the number of colours in the image, which is ideal for logos, screenshots and flat graphics but not for photographs with smooth gradients.

WebP typically saves 25 to 35 percent over JPG at similar quality and keeps transparency. AVIF can save even more but takes longer to encode, so batches of large photos will be slower.

Good to know

• Compressed images have their metadata removed, including GPS position and camera details. The rotation is applied to the pixels so photos still appear the right way up.
• Compressing a JPG that has already been compressed hard gives smaller gains and can add visible artefacts. Start from the original when you can.
• If you only need smaller dimensions, the resize tool often saves more than quality reduction alone. To hit an exact limit, use compress to 100 KB.
• Screenshots and diagrams usually compress best as PNG or lossless-looking WebP, while photographs do best as JPG, WebP or AVIF.