JPG compressor
Nothing is uploaded; every file is processed in this browser
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.
How to compress a JPG
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.
Questions
Around 75 for web use, 85 or higher for anything printed. Below 60 the artefacts become visible.
Yes. JPEG is lossy and the losses compound, so always work from the original.
Typically half at quality 75 from a camera JPEG. Capping the dimensions can cut it by 90% or more.
Usually 25–30% smaller at matching quality, with near-universal browser support now.
As many as you like. It runs in your browser, so there is no upload and no limit.