Is this photo compressor really free?
Yes. There is no account, no limit on how many photos you compress, and no mark of ours on your photos. It is made by Capturely, a client gallery service for photographers, and costs nothing to use.
Are my photos uploaded anywhere?
No. The photos are compressed by your own browser, on your device. They are never sent to a server, and they are gone when you close the page. Only your last settings (quality, target size, longest edge) are remembered on this device.
Will I see a difference after compression?
At High and Balanced you should not, at normal viewing size on a screen. Small file gives up a little fine detail for a much lighter file, which is fine for email and web pages. The preview shows each finished photo, so you can check it before you download, and your originals are never changed.
How does the target size work?
Choose a limit such as 500 KB, 1 MB or 2 MB. The tool encodes each photo at several qualities between 92 and 40 and keeps the highest one that fits. It does not go under 40, where a photo starts to look damaged: if a photo still does not fit, the tool tells you, and setting a longest edge will get it there.
Which formats can I compress?
JPEG, PNG and WebP. A JPEG stays a JPEG and a WebP stays a WebP (Safari cannot save WebP, so there it becomes a JPEG). PNG has no quality setting, so a PNG is saved as a JPEG on a white background, which is far lighter for a photograph. Camera details such as EXIF data are not copied into the new file.
Why did one of my photos not get smaller?
It was already compressed as far as your setting goes, so saving it again would cost quality and gain nothing. The tool leaves such a photo alone and hands you the original back.