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How this compresses without uploading anything
Most compressors send your file to a server, shrink it there and send it back. This one does not. Your browser already ships with a JPEG and WebP encoder, and this page simply asks it to re-save your image at the quality and width you pick.
That has one consequence worth stating plainly: there is no upload, so there is nothing to leak, nothing stored and nothing to delete afterwards. You can confirm it — open your browser's network tab, compress a file, and watch that no request goes out.
It also means the tool works offline once the page has loaded, and that a 20 MB photo does not have to travel twice across your connection before you see the result.
WebP or JPEG: which one to pick
Google reports that lossy WebP files come out 25 to 34 % smaller than a JPEG of comparable quality. WebP is supported in every current major browser, so for anything going on a website it is the better default, and it is what this tool selects for you.
JPEG is the right choice when the file has to be opened by something older or fussier — a print shop, a marketplace that rejects WebP, an internal system nobody wants to touch. It is a little heavier at the same quality, and universally accepted.
One thing this tool will not pretend to do: if you feed it a PNG and ask for a PNG back, almost nothing happens. PNG is a lossless format, so there is no quality dial to turn. To make a PNG meaningfully lighter you have to change format, which is why WebP is offered instead.
How far to push the quality slider
Quality 80 is the setting to start from. On photographs it typically removes most of the weight while leaving nothing you would notice on a screen. Below about 60 the damage starts to show on skies, skin and flat gradients — the smooth areas go blotchy first.
Screenshots, logos and anything with sharp text behave differently. Lossy compression smears the edges of letters, so those want a higher setting, or a format built for flat colour.
The honest way to use the slider is to move it and look at the result, rather than trusting a number. Compress the same file at 80 and at 60, open both, and decide with your own eyes which one you would be happy to publish.
Why width usually matters more than quality
A photo straight from a phone is often 4.000 pixels wide. The place it ends up — a product card, a blog post, a category listing — might draw it at 600. Every pixel beyond what the screen actually paints is weight nobody sees.
Resizing before compressing is the single biggest saving available here, and it is why the tool offers a maximum width alongside the quality slider. Set it to something close to the size the image will really be displayed at, and the quality setting matters far less.
Doing this once is easy. Doing it forever is the problem
Compressing a handful of files by hand works fine. It stops working when the images arrive every week, when somebody else uploads them, or when the same picture has to exist at four different sizes for four different screens.
That is the job NimboCDN does on a WordPress site: it prepares each image at the size the visitor's screen will actually draw, in the format their browser accepts, and serves it from our side instead of yours — as WebP on the free plan, and AVIF on Pro, which is usually lighter still. You install the connector and the delivery changes; nothing in your library is rewritten.
If you want to know whether it is worth it for your site, the image size checker measures the bytes your pages send today and estimates what they would weigh afterwards.
Questions
Are my images uploaded anywhere?
No. The compression runs in your browser, on your device. There is no upload and no copy on our side — you can verify it in the network tab of your browser's developer tools.
Is there a limit?
Twenty files at a time, up to 25 MB each. The limit is there because the work happens on your own device, and a phone with twenty large photos open at once runs out of memory.
Why is my PNG barely smaller?
PNG is lossless, so re-saving it as PNG has almost nothing to remove. Choose WebP instead and the same picture usually drops a great deal.
Does it keep my EXIF data?
No. Re-encoding drops the metadata, including GPS coordinates and camera details. For publishing on the web that is usually welcome, but keep your originals if you need that information.
What about animated GIFs?
Only the first frame survives, so this is not the right tool for them. An animation is almost always better off as a video file.
Do I need an account?
No. No account, no email, no credit card. The page does not know who you are.