Compress Image to 100 KB

How much detail fits in 100 KB?

The tool treats 100 KB as 100,000 bytes, which is 800,000 bits. How good the image looks depends on how many pixels have to share that budget. Divide the bits by the pixel count and you get bits per pixel — the best single predictor of whether a photo will survive the squeeze.

For ordinary photos, roughly 1.5 bits per pixel or more looks excellent, around 0.7 still looks clean at normal viewing size, and much below 0.4 starts to show blocks and smeared detail.

Where 100 KB limits come from

Online application portals — exam registrations, job applications, visa and ID forms — commonly cap photo uploads somewhere between 20 KB and 100 KB, and signature scans are often limited further still. The limits exist because these systems store and review huge numbers of submissions, not because a small file is better.

Such forms usually specify pixel dimensions or a print size as well as a file size. Meet the dimensions first (the Resize Image for Passport Photo tool covers the common 35 × 45 mm and 2 × 2 inch formats), then bring the file under 100 KB here. Done in that order, a face photo normally fits with quality to spare.

If the portal still says the file is too big

• Kilobytes are counted two ways: 1,000 bytes on some websites and 1,024 on others. This tool aims for the stricter reading — at most 100,000 bytes — so the file is under the limit whichever way the site counts.
• Check the format the site accepts. The output is always a JPG; if a form insists on PNG, a 100 KB PNG photo is rarely possible because PNG cannot discard detail.
• Make sure you're uploading the compressed download and not the original — on a phone, both copies can end up side by side in the same folder.

Compressing a signature scan

Signatures are mostly white paper with thin dark strokes, which compresses extremely well once the empty space is gone. Crop tightly around the signature before compressing, photograph it on plain white paper in even light, and keep your phone's shadow off the page — shadows add grey texture that costs bytes and looks messy on the form.