Compress images in bulk
Shrink hundreds of images at once without visible quality loss. Runs entirely on your device.
or click to browse · JPEG, PNG, WebP, AVIF
Downloading more than one file produces a .zip archive.
How image compression actually works
Image compression is not magic — it is a set of trade-offs. Understanding which knob does what is the difference between halving your page weight and turning photographs into mush.
Lossy versus lossless
Lossy compression (JPEG, WebP, AVIF) throws away detail your eye is unlikely to notice, then stores what remains more cleverly. This is why a JPEG can be a tenth the size of the original while looking almost identical. Lossless compression (PNG, and lossless WebP) keeps every pixel exactly; it can only shrink files so far, but nothing is degraded.
The practical rule: photographs and anything with smooth gradients go lossy. Screenshots, diagrams, logos and text go lossless — lossy compression smears sharp edges and makes small text look dirty.
What the quality slider really does
The quality value does not mean "percent of the original quality". It selects a quantisation table: how coarsely the encoder rounds off the frequency data it stores. Because of how human vision works, the relationship is not linear. The useful landmarks:
- 90–100% — nearly indistinguishable, but files stay large. Rarely worth it outside print workflows.
- 75–85% — the sweet spot for photographs. Most people cannot tell the difference in a blind test, yet files typically shrink by 60–80%.
- 50–70% — visible softening on close inspection. Acceptable for thumbnails and previews.
- Below 50% — blocky artefacts and colour banding. Only justified when file size is the only thing that matters.
Choosing an output format
| Format | Best for | Transparency | Browser support |
|---|---|---|---|
| JPEG | Photographs, when maximum compatibility matters | No | Universal |
| PNG | Screenshots, logos, text, anything with sharp edges | Yes | Universal |
| WebP | Almost everything — 25–35% smaller than JPEG at equal quality | Yes | All modern browsers |
| AVIF | Maximum compression, roughly 50% smaller than JPEG | Yes | Modern browsers; encoding support varies |
If you are optimising a website, WebP is the safe default and AVIF is the aggressive one. Serve both with a <picture> element and let the browser pick.
Why dimension matters more than quality
Here is the thing most people miss: halving the width and height of an image removes 75% of the pixels. That single change almost always beats any amount of quality tuning. If you are shipping images to a website, resize to the largest size actually displayed — and only then worry about quality. A 4000-pixel-wide photo displayed in an 800-pixel column is pure waste, no matter how tightly you compress it.
Does this tool change your originals?
No. Your source files are never modified. Each processed image is produced as a new file in your browser's memory and handed back to you as a download. Your originals on disk are untouched.