Free image compressor.
Reduce photo file size by changing export format or quality, optionally shrinking oversized images, then download the result.
Export WebP, JPEG or PNG with your chosen quality. Optionally shrink oversized images first.
Images stay on your device. Browser export support varies: PNG ignores the quality slider, JPEG turns transparency white. Compression does not always mean a smaller file; check the actual result.
How to use this tool
- Choose a PNG, JPG or WebP file. We process it in your browser.
- Select the output format and quality. Optionally cap the maximum width or height.
- Compress and compare the original and output sizes. Download when the result looks right.
Good to know
PNG uses lossless output so a PNG file may not shrink. JPEG removes alpha transparency and can introduce compression artifacts. File size depends on image detail; quality settings do not guarantee savings.
This utility processes its content locally in your browser. No usage counter is required while public tools are free and unlimited. As with any online tool, avoid entering sensitive information on devices you do not trust.
What does image compression actually do?
There are two simple levers: the number of pixels and the amount of detail retained during encoding. If a camera photo is 5000 pixels wide but your website displays it at 1200, reducing dimensions can remove a lot of unnecessary data. Lowering JPEG or WebP quality can remove more bytes, though very low settings may make fine detail look smeared.
Start with a reasonable quality setting, inspect the result visually and compare the measured file sizes. Different photos compress differently; a flat illustration and a textured portrait will not produce the same savings.
Why a PNG might become larger
PNG is lossless and does not obey the JPEG/WebP quality slider. A browser's PNG output can even be larger than the original if the original file was already optimized or used a compact color palette. A bigger result is not a failure in your measurement; it tells you that this output choice did not help.
Try WebP for photographs or visuals that benefit from lossy compression. Keep PNG when you need exact pixels and transparent graphics and the additional bytes are worth it.
Check the right things before publishing
Look at width, height, original bytes and exported bytes. An oversized hero can slow down a page, but an aggressively compressed hero that looks ugly will not improve the experience. Size is one part of a fast page; caching, responsive images and network conditions also matter.
The tool reports the final file size and whether it is larger or smaller. Everything stays on your device until you upload the download elsewhere.
Questions about free image compressor
Does this tool upload my images?
No. The original file is opened and processed locally by your browser. RezSat does not receive the image pixels.
Why is the compressed file bigger?
Changing format or re-encoding can produce a larger output, especially with PNG or already optimized files. Try WebP, reduce dimensions or compare quality levels.
What format should I use for website photos?
WebP is a useful modern default for many photos. JPEG is broadly compatible. Choose based on visible quality, browser support and measured bytes, not just the extension.