How to Compress an Image Without Making It Look Bad

What does image compression do?

Image compression reduces the amount of data needed to store an image. The goal is usually to make uploads, websites and sharing faster while keeping the picture looking acceptable.

Compression does not necessarily mean changing the image dimensions, although resizing can also reduce file size.

Want to try the idea yourself? Use the Image Compressor.

Lossy vs lossless compression

Lossy compression removes some image information to achieve smaller files. JPG commonly uses this approach. At sensible settings the difference may be hard to notice, but heavy compression can create blur or blocky artefacts.

Lossless compression reduces file size without discarding image information, although the possible saving is often smaller. PNG commonly uses lossless compression.

If you want to explore this topic further, see How to Resize an Image Without Distorting It.

Start with the intended use

A large photo for print needs more detail than a small image displayed inside a web page. Compressing to the final purpose avoids keeping unnecessary data.

If an image will only appear at 800 pixels wide, storing a 6,000-pixel original for that web use may be unnecessary.

How to judge quality

Look at detailed areas such as faces, text, hair, edges and gradients. Compression problems often appear there before they are obvious in simpler parts of the image.

Compare the result at the size people will actually view it, not only at extreme zoom.

Compress and compare

The Image Compressor lets you reduce image size and compare the output before using it. Keep the original if you may need to edit or export it again later.

Repeatedly saving an already compressed JPG at lower quality can compound quality loss, so it is better to make new versions from a good source file.