How to compress an image without losing visible quality

“No visible loss” is more realistic than “no loss”

In formats with lossy compression, reducing the file means discarding information. The practical goal is that this loss is not perceptible in final use. For an image that will be viewed on a small screen, the acceptable point may be different than for a photograph intended for printing.

Start with the most conservative level

Process with low compression first. If the savings are enough, you're done. If not, move to a balanced level and compare again. This approach avoids degrading more than necessary.

Zoom into difficult areas

Review fine print, fine lines, hair, textures, and gradients. Those parts reveal compression artifacts earlier. A thumbnail can look perfect while when enlarged, defects appear.

Don't recompress again and again

If you can, always go back to the original file when testing configurations. Compressing a file that has already been compressed can accumulate degradation.

Choose the appropriate format

Quality does not depend solely on percentage. A graphic with transparency may need PNG, while a photograph may get a better appearance-weight ratio at JPG or WebP.