Compress images

Keep the original if you are unsure. WebP is typically 25 to 35 percent smaller than JPEG at the same visible quality and works in every current browser. AVIF is smaller still but takes longer to encode and is not supported everywhere. PNG is lossless, so quality has no effect on it and only resizing will make it smaller.

JPEG has no transparency, so the transparent areas become white. The tool checks whether your image actually uses its alpha channel and tells you when this has happened - it is exactly right for a photograph and ruins a logo.

Yes, always. Re-encoding through the browser's canvas drops every piece of metadata, including the camera model, the timestamp and the GPS coordinates a phone attaches to a photograph. There is no option to keep them, because a photo about to be sent somewhere is not the place for your home address.