Lossy vs Lossless Image Compression
This guide is about choosing how to compress: accepting some loss for a much smaller file, or keeping every pixel. For a comparison of the formats themselves, see JPG vs PNG vs WebP: Which Image Format Should You Use?.
The difference
Lossless compression stores the image in fewer bytes without changing a single pixel; decoding gives back exactly the original. Lossy compression throws away detail the eye is unlikely to notice, such as fine texture and subtle color shifts, and stores an approximation. The quality setting controls how much is thrown away.
What each does to different images
| Image | Lossless | Lossy |
|---|---|---|
| Photo | Large files: camera noise is hard to compress exactly | Often several times smaller at a quality that looks the same |
| Screenshot, text, interface | Small and sharp | Can blur text and add speckles around edges |
| Logo, flat graphic | Very small, crisp edges | Edges may smudge or ring |
| Transparent cut-out | PNG or lossless WebP | Lossy WebP keeps alpha; JPG can’t |
Which formats do which
- JPG is always lossy.
- PNG is lossless. Reducing a PNG to a 256-color palette, as Compress PNG can, is a lossy step before the lossless encoding.
- WebP can be either, depending on how it was saved.
Repeated lossy saves add up
Every time a JPG or lossy WebP is opened, edited and saved again, it is re-compressed and loses a little more. One or two saves at quality 85 or above are rarely visible; many rounds produce blockiness and color banding. Keep a lossless master (a PNG, or the camera original) and export a lossy copy once, at the end. Converting a JPG to PNG stops further loss but doesn’t undo what is already gone.
Choosing a quality
- 85–92: hard to tell from the original; good for photos you care about.
- 75–80: a good default for websites and email.
- Below 70: visible softness and blockiness, especially in skies, skin and text.
If a file is still too big at 75, reduce its pixel dimensions rather than pushing the quality lower; see How to Reduce Image File Size Without Making It Look Bad.
Quick decision
- Need exact pixels, sharp text or a master copy: lossless (PNG).
- Photo for sharing or the web: lossy (JPG or WebP) at 75–85, with Compress JPG or Compress WebP.
- Graphic with transparency for the web: WebP, or PNG where WebP isn’t accepted.