ResizeKB is a free, single-purpose tool for one of the internet's most annoying small problems: online forms that demand images under an exact kilobyte limit. Job portals, visa applications, university admissions, government services, and marketplaces all impose these limits, yet almost none of them offer any help in actually meeting them. We built the tool we wanted to use when a form says "photo must be under 100 KB."
The idea is simple: you state the exact target size in kilobytes, and the tool delivers a file at or under that size. Instead of the usual low, medium, and high quality guesses, our compressor measures real output bytes at every step of a binary search across JPEG quality levels, converging on the highest quality that fits your budget. When quality reduction alone cannot reach an aggressive target, an optional resizing step trims pixel dimensions progressively, and if the target is truly unreachable, the tool says so honestly rather than handing back a file that would fail the upload check anyway.
Privacy is the design, not a feature. ResizeKB has no backend for images: every upload box on this site is a doorway into your own browser's memory, never onto the network. Your photos, ID documents, signatures, and scans are decoded and re-encoded by your device using standard browser APIs, and they are discarded the moment you close or reset the page. The only thing we store is a single preference in your browser's local storage — the last target size you used — so the slider starts where you left it. Even that stays on your device.
The site covers the whole small workflow: a compressor with presets for the most common limits (20 KB and 100 KB), variant pages for the ways people phrase the task, and a size checker that measures any image's exact kilobytes, bytes, and pixel dimensions before or after compression. Everything works on mobile as well as desktop, in any modern browser, with no account and no usage cap. ResizeKB is supported by clearly labeled advertising and nothing else — no subscriptions, no premium tiers, no watermarked "free" output.