JPG compressor

JPEG compression discards detail the eye is least sensitive to. Re-encoding at quality 75 typically halves a camera JPEG with no visible loss. Capping the longest side saves considerably more if the image is larger than it needs to be.

Every JPEG re-encode loses a little more, and the losses accumulate — a file compressed five times looks visibly worse than one compressed once at the same final quality. Always compress from the original rather than from an already-compressed copy, and keep the original if you might need a different size later. Generation loss is the reason a picture reposted repeatedly on social media ends up looking the way it does.