Why compress pictures
Phone photos are often 3–8 MB, which is too large for many upload forms, slow to send over mobile data and heavy for websites. Compressing reduces the file size while keeping the picture looking almost the same, so it uploads and loads quickly.
How the settings work
The Quality slider (10–95, default 70) controls how strongly the picture is compressed — lower means smaller files. The maximum width shrinks very large photos to a sensible size, which saves even more space. With “Keep original format”, PNG and WEBP files stay in their format; otherwise the result is a JPG. If you enter a target size in KB, the tool searches for the best quality that fits under that size and saves a JPG.
What to expect
Typical phone photos can often shrink by 70–90% at quality 70 with a width around 1600 pixels, with no difference visible on a phone screen. Pictures that are already small or already heavily compressed may not shrink much — if compressing does not make a file smaller, you get your original back instead of a worse copy.
Common problems and how to fix them
The picture looks blocky: raise the quality to 80–85. Still too big for a form: enter the form's KB limit in the target size box, or use Resize Image to 20KB, 50KB or Resize Photo to 100KB. Transparent PNG turned white: transparency is lost when saving as JPG; keep the original format option on and leave the target KB empty.
Good habits
Compress copies and keep your originals, check one picture at full size before compressing a whole batch, and remove location data with Remove Image Metadata before posting photos publicly.