Use the limit as a ceiling, not a guess
If a form says 100 KB, enter 100 KB rather than aiming for a vague percentage reduction. Leave a small margin when the service is especially strict, because some systems count file metadata or reject files that sit exactly on the stated limit.
Choose JPG or WebP for photographs. PNG is lossless and is usually a poor fit for a small fixed limit unless the image is a simple graphic, logo or screenshot with few colors.
- Profile or registration image: often 100 KB or 200 KB
- Email attachment or chat upload: check the service limit before exporting
- Website image budget: choose a target based on the image's display size, not only the upload limit
Preserve dimensions until the limit requires a reduction
Quality should be the first adjustment for a photograph. Lowering it a little can remove many bytes without changing the displayed dimensions. When even a low quality setting is too large, the source contains more pixels than the limit can support, so reducing width and height is the honest next step.
Inspect text, faces and high-contrast edges after exporting. If the result is too soft, use a slightly higher target, crop away unused background, or start from a smaller source image before compressing again.
Keep the source and verify the downloaded result
Do not overwrite the only original image. Save a copy for future edits, then upload the downloaded result to the destination service. The final test is whether that service accepts the exact file you exported.
For private documents and personal photos, a browser-local tool avoids sending image contents to a processing server. The result is still created on your device, so closing the tab or choosing a new file clears the temporary browser copy.