What compression actually changes
Compression attacks the same problem from two directions. Lossless methods look for repeated patterns and store a short description instead of the raw pixels, so the decoded image matches the original exactly.
Lossy methods go further and remove information the eye is unlikely to notice. Detail in smooth areas goes first, which is why a heavily compressed photo looks softer up close while still reading well at normal size.
Choosing between lossy and lossless
Photographs usually do better with lossy compression, because smooth gradients give the encoder room to work. Logos, screenshots, and text need lossless handling so edges stay sharp and legible.
A useful habit is to compress once and check the result, rather than saving repeatedly. Each extra pass on a lossy file compounds the damage from earlier saves.
- Compress photographs with lossy settings for the biggest savings
- Keep screenshots and line art lossless to protect sharp edges
- Check pixel dimensions as well as byte size
- Compare the result against the original before you publish
Compressing images in the browser
Filekind compresses JPEG and PNG input and writes a JPEG at or below the limit you enter in KB or MB. The file is processed locally, so it is never uploaded to a server.
Inputs up to 25 MB, 16,000 pixels per side, and 48 megapixels are accepted. If a target is unusually small, the tool may reduce dimensions to reach it, and it reports the final size and dimensions before you download.