Image compressor
Shrink photos without uploading them. The file never leaves your device.
Runs entirely in your browser. Nothing you enter is uploaded.
How this works
Resize first, then compress
The single biggest saving usually has nothing to do with the quality slider. A photo straight from a modern phone is often 4,000 pixels across. Displayed at 800 pixels wide on a web page, three quarters of every dimension is thrown away by the browser anyway — you paid to transfer pixels nobody ever saw.
File size scales with area, not with width. Halving the longest edge quarters the pixel count, and the file usually follows. That is a far larger reduction than moving quality from 90 to 75, and it costs nothing visible if the image is displayed at the smaller size.
A practical order of operations:
- Decide the largest size the image will ever be displayed at.
- Resize the longest edge to about twice that, for high-density screens.
- Then, and only then, adjust quality.
What the quality setting actually does
Lossy formats work by discarding detail the eye is bad at noticing — fine colour variation especially, since human vision is far more sensitive to brightness than to hue. The quality number controls how aggressively that discarding happens.
| Quality | What you get |
|---|---|
| 90–95 | Visually identical to the original. Large files. For archiving or print. |
| 75–85 | The usual choice for the web. Differences are hard to see side by side. |
| 60–75 | Small files. Artefacts appear in gradients such as skies. |
| Below 60 | Visible blocking around edges. Only for thumbnails. |
Compression is not reversible. Each save at a lossy setting discards detail permanently, so repeatedly editing and re-saving the same JPEG degrades it a little each time. Always compress from the original, not from a previously compressed copy.
Choosing a format
WebP is the default worth reaching for. It compresses better than JPEG at the same perceived quality, supports transparency, and works in every current browser. The main reason to avoid it is a system elsewhere in your workflow that will not accept it.
JPEG remains the safest interchange format. Anything that reads images at all reads JPEG. It cannot store transparency, which is why this tool fills transparent areas with white when you convert to it — otherwise they would come out black.
PNG is lossless. That makes it the correct choice for screenshots, logos, charts and line drawings, where lossy compression smears the sharp edges into visible mush. It is the wrong choice for photographs, where it often produces a file several times larger than the JPEG it replaced.
Why local processing is the better arrangement
Most compression sites work by uploading your file, processing it on a server, and returning a download link. That means a copy of your image existed on someone else's machine, subject to their retention policy, their access controls, and their breach history. For a holiday snapshot that may not matter. For a passport scan, a medical document, or an unreleased product photo, it very much does.
Browsers have been able to decode, resize, and re-encode images natively for over a decade. Sending the file away was never technically necessary — it was just easier to build. Processing locally is also faster, because there is no upload wait and no queue, and it works with several files at once without a size cap imposed by someone's bandwidth bill.
Common questions
- Is my photo really not uploaded?
- Really not. The compression uses your browser's own image encoder through a canvas element — the same code that renders every image you see on the web. You can confirm it: open your browser's network inspector, compress a file, and watch that no request is made. Disconnect from the internet after the page loads and the tool still works.
- Which format should I choose?
- WebP for almost everything on the web — it is typically 25–35% smaller than JPEG at matching visual quality and is supported everywhere that matters. JPEG when something downstream will not accept WebP. PNG only for screenshots, diagrams, and anything with sharp edges or transparency, where lossy compression leaves visible artefacts.
- Why did my PNG get bigger?
- PNG is lossless, so re-encoding a photograph as PNG stores every pixel exactly and often produces a larger file than the JPEG you started with. If a photo grows, switch the output to WebP or JPEG. PNG is the right choice for flat graphics, not for photographs.
- What quality setting should I use?
- Around 75 is the usual sweet spot: most people cannot see the difference from the original at normal viewing size, and the file is a fraction of the size. Below 60, edges and gradients start to show blocking. Above 90, the file grows quickly for very little visible gain.
- Does compressing remove EXIF data?
- Yes, as a side effect. Redrawing through a canvas keeps only the pixels, so camera settings, timestamps and — importantly — GPS coordinates do not survive. That is usually welcome before posting a photo publicly, but do keep an original if the metadata matters to you.