Large images slow downloads and make uploads harder. Compression helps, but aggressive settings can blur faces, text, and product edges.
Upload the image you want to shrink and begin with a balanced quality value. Compare the before and after preview instead of guessing from the file size alone.
Photos usually tolerate more compression than screenshots or UI mockups. Keep screenshots closer to the higher end of the quality range so thin lines stay readable.
If you need a specific target size for email or a form upload, compress in steps and stop once you reach the limit with an acceptable preview.
Save the compressed file with a clear name so you can keep the original as a backup for future edits.