Compress images online, without uploading them
Drop a photo into the editor above and watch the output size fall as you move the quality slider. The work happens on your own device — no upload, no account, no watermark.
What compression actually throws away
A lossy encoder does not shrink a picture by storing the same thing more cleverly. It decides which parts of the image you will not miss, and stops recording them. Three mechanisms do most of the work:
- Chroma subsampling. Human vision resolves brightness far more finely than colour, so the encoder keeps full detail in luminance and records colour at half resolution. This is nearly invisible on photographs and very visible on red text against a dark background — which is why screenshots of code compress badly as JPEG.
- Quantisation. The image is broken into blocks, each block is converted into a set of frequency coefficients, and the fine, high-frequency ones are rounded off. The quality slider is essentially choosing how aggressively to round. Round too hard and the blocks stop agreeing with their neighbours, which is what blocking artefacts are.
- Precision in smooth areas. A clear sky is a very gentle gradient. Once quantisation coarsens it, the gradient becomes a series of steps — banding. It is the first artefact most people notice, and the reason images with large flat areas need a higher quality setting than busy ones.
None of that is reversible. An exported file cannot be un-compressed back to its original quality, so keep your originals and treat the export as a delivery copy.
What savings to expect
Results vary with the picture, but these are the ranges you will usually see going from a camera JPEG at default settings:
| Source | Export | Typical saving | Watch out for |
|---|---|---|---|
| Photograph, JPEG | WebP quality 80 | 25–35% | Sky and skin gradients |
| Photograph, JPEG | JPEG quality 80 | 10–40% | Re-compressing an already lossy file |
| Screenshot, PNG | WebP quality 90 | 50–80% | Text edges going mushy |
| Logo or line art, PNG | PNG | 0% | Lossy formats ruin hard edges |
| Phone photo, 12 MP | Resize to 1600 px, then WebP 80 | 90%+ | Nothing — this is the big win |
That last row is the one worth internalising. Resizing beats compressing. A 12-megapixel photo displayed in a 1600-pixel-wide column is carrying about five times more pixels than it can ever show, and no quality setting recovers the bytes that resizing gives back for free. Resize it first, then compress.
Settings for the job in front of you
An image for a web page
Resize to the widest size it will actually be displayed at — double that if you are supporting high-density screens — then export WebP at quality 75–85. For a typical content image that lands somewhere between 40 and 150 KB.
A photo to email
Mail servers commonly reject attachments over 10–25 MB, and recipients on phones will thank you for far less. Resize the long edge to 2000 px and export JPEG at 80: recognisable on any device, openable by any software written in the last thirty years, and usually under 500 KB.
An upload form with a hard limit
Do not guess. Switch on Compress to a maximum file size, type the limit, and let the editor search the quality range for the largest setting that fits. There is a page dedicated to the 100 KB case, which is the limit most forms use, and one for 50 KB, where the dimensions matter even more.
When not to compress at all
Lossy compression is the wrong tool for anything where the exact pixels are the content: a screenshot that someone will read text from, a logo that has to sit on a brand background, a diagram with thin lines, a QR code. For those, export PNG — or WebP at quality 100, which the browser writes as lossless WebP and which is frequently smaller than the equivalent PNG while staying pixel-exact.
More image tools
Every one of these is the same editor, opened for a different job — and all of them run on your device.
- Compress to 100 KBHit a hard upload limit without guessing at the quality slider.
- Resize an imageChange the pixel dimensions with Lanczos3, Catmull-Rom or Mitchell.
- Crop an imageTrim to what matters, freeform or to a fixed ratio.
- PNG to WebPSame picture, same transparency, a fraction of the bytes.
- Remove EXIF dataStrip the GPS location, camera and serial number from a photo.
Or start from the full editor, which does all of it at once.