Image compression tools
Two ways in: pick the kilobyte limit an upload form is enforcing and let the tool find the best quality that fits, or compress by quality when you just want a lighter file for the web.
Free · run in your browser · nothing uploaded
Get under an exact size limit
For application, exam and visa portals that reject anything over a number.
Compress by quality
For websites, email and storage, where smaller is better but there is no hard limit.
Compressing a PDF instead?
About these tools
Compression tools exist because upload forms and web pages both have limits, and the two want different things. A form wants a file under a specific number of kilobytes and does not care how it looks; a web page wants the smallest file that still looks right at the size it is displayed. The tools here cover both: pick a quality level when you are optimising, or set a target size when a form is enforcing one.
Everything runs in your browser, which matters more for compression than for most tasks. The files people compress are photographs of themselves, scanned identity documents and screenshots full of account details — precisely the files worth not handing to a server. The site imposes no daily processing quota, but browser memory and image dimensions still limit which files your device can handle.
Questions people ask
The form says the limit is 100 KB. Which tool do I use?
Compress image to 100 KB. It re-encodes the photo at progressively adjusted quality until the file is under 102,400 bytes (100 × 1,024), and only shrinks the pixel dimensions if quality alone cannot get there. A few portals count a kilobyte as 1,000 bytes; if one rejects a file that is just under the limit, open Options in Compress image and set a target a few KB lower.
Why does my image get smaller in pixels, not just in bytes?
Very tight targets such as 20 KB cannot always be reached by lowering quality alone — a large photograph at the lowest quality is still too big. When that happens the tool scales the dimensions down until it fits. Resizing the image yourself first, to the size the portal actually displays, usually gives a sharper result.
Should I compress a PNG or convert it to JPG?
If it is a photograph, convert it: JPG stores photos five to ten times smaller than PNG. If it is a screenshot, logo or anything with transparency, keep it as PNG and use Compress PNG, which reduces the colour palette while keeping transparency intact.