Read the limit and the dimensions together
Before compressing a photo, write down the accepted format, the permitted pixel dimensions and any minimum or maximum file size. A form may reject a picture because it is too small as well as too large. Making the smallest possible file is therefore the wrong target.
For example, US visa digital-image guidance specifies JPEG and a maximum of 240 kB, alongside its dimension requirements. Do not apply that limit to every passport or ID application. Use the limit shown for the particular form you are completing.
Prepare from the full original
Make a working copy and keep the untouched source. Start with any required crop, but only if the application allows or requires you to crop before uploading. Resizing a badly framed picture does not fix the position of the face.
If an image is thousands of pixels wider than the requested output, reducing its dimensions to an allowed size can save substantial space. Preserve the correct aspect ratio. Do not force a rectangular image into a square by changing width and height independently, because that stretches the face.
Use compression after the dimensions are right
Export a JPEG copy and check the saved byte size. If it is still above the limit, lower the quality gradually and inspect each result. Look around the eyes, hair and high-contrast edges for blocky patches or smeared detail. Stop when the file meets the limit with a clear result, rather than continuing until it is tiny.
Return to the original working copy for each export. Reopening an already compressed file and saving it repeatedly adds another variable to the process. A single controlled export is easier to compare and undo.
Verify the file that will actually be uploaded
Open the final saved copy, not only the editor’s preview. Confirm its format, pixel dimensions, orientation and size. Some systems display rounded file sizes, so leave a modest margin below a strict maximum rather than aiming for the last displayed kilobyte.
Do not strip out so much detail that the face becomes soft just to pass a byte check. If a correctly sized image remains difficult to compress cleanly, check whether you began with a screenshot, scan or noisy low-light capture. A better source may be the effective fix.
Sources and further reading
US Department of State · Digital visa image requirements ↗Apple Support · Crop, resize or rotate an image in Preview ↗Requirements can change. Check the official instructions for your application before submitting.
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