Change DPI
Set the print resolution: 72, 96, 150, 300 or your own value. The pixels do not change. Everything happens in the browser, files are not uploaded anywhere.
JPG, PNG and BMP are changed without recompression: pixels and quality stay the same, only the DPI value is written. Other formats have to be re-saved.
DPI shows how many dots of the image fit into an inch when printing. The pixels themselves do not change: only the record in the file changes, and the size of the printout in graphics and office programs depends on it.
For printing photos the usual value is 300 DPI, documents and scans often need 150 or 200, and for the screen 72 or 96 is traditionally given. Choose a preset or enter your own number from 1 to 65,535.
JPG, PNG and BMP files are changed without recompression: the pixels stay the same, the quality does not drop and the file size barely changes. The page writes the resolution into the standard fields of the format and updates the EXIF values if they already exist.
Other formats, such as WebP, AVIF, GIF or TIFF, do not store DPI in the usual way, so they have to be re-saved as PNG or JPG. Animated files are skipped so that no frames are lost.
Next to the result you see the print size in centimeters, so you can tell at once whether the image suits the format you need. Processing happens in the browser, files are not uploaded to a server, and the finished images can be downloaded one by one or all at once.