How compression works here
Your image is drawn onto an in-browser canvas and re-encoded as a JPEG at the quality level you choose, which reduces file size by simplifying color and detail data. Lower quality settings produce smaller files but can introduce visible artifacts, so it's worth comparing the preview before downloading.
When to compress images
Smaller image files load faster on websites, take up less space in emails and messages, and upload more reliably on slow connections. This is especially useful before adding photos to a website, since large uncompressed images are one of the most common causes of slow page load times.
Frequently asked questions
Will compressing my image make it look noticeably worse?
At moderate quality settings (60–85%), most photos show little to no visible difference while file size drops significantly. Very low quality settings (under 30%) can introduce visible blocky artifacts, especially in areas with fine detail.
Can I compress PNG files, or only JPG?
You can upload PNG, JPG, or WebP files. The compressed output is saved as JPG, which is the format best suited to quality-based compression — this means transparency in PNG files will be replaced with a white background.
Is there a file size limit?
There's no hard limit set by the tool, but very large images (many megapixels) may take a moment longer to process since everything runs on your device rather than a server.
Does compressing an image reduce its pixel dimensions?
Generally no — compression here reduces file size through encoding quality, not pixel dimensions. The one exception is a very high-resolution photo (well beyond typical camera output) which may be scaled down slightly to stay within limits mobile browsers can safely process. If you specifically need to resize width and height, use the Image Resize & Crop tool instead, which includes quality control too.
Why does it say "Already optimal" instead of a percentage?
Some images — particularly PNG screenshots and photos that have already been compressed elsewhere — don't shrink further when re-encoded, and can occasionally come out larger. This tool checks for that and automatically keeps your original file whenever re-encoding wouldn't actually help, rather than handing back something bigger than what you uploaded.