Keep the ratio, or knowingly break it
Type a width and the height follows on its own, because a stretched photo is the most common way a resize goes wrong. The proportions are locked by default and the original dimensions stay on screen so you always know what you started from.
Untick the box only when you genuinely want a fixed frame — a banner slot, an avatar box, a thumbnail grid — and accept that the image will be squashed to fit.
Resizing down is safe, resizing up is not
Shrinking an image throws away pixels and looks clean. Enlarging invents them, and no amount of processing brings back detail that was never captured. A 400 px wide photo blown up to 1600 px will look soft whatever tool you use — this one included. If you need a bigger image, go back to the original file rather than upscaling a small copy.
Frequently asked questions
Which formats can I resize?
JPG, PNG and WebP. The result is produced as a PNG so that transparency is never lost.
Will resizing reduce the file size?
Usually yes, because there are fewer pixels to store. If you specifically want a smaller file at the same dimensions, use the compression tool instead.
Can I resize several images at once?
Not for now — this tool handles one image at a time so you can check the result before downloading.
Is my image sent to a server?
No. Everything happens in your browser.