Resize Image to 20KB Online

What Fits in 20 Kilobytes

20 KB is 20,480 bytes. A JPEG of an ordinary photograph costs somewhere between a quarter and a half a byte for every pixel it stores, so 20 KB buys roughly 50,000 to 80,000 pixels in total - about 300 by 230. That is the honest arithmetic behind this page: a 12 megapixel phone photo cannot become a 20 KB file and stay 12 megapixels. Something has to go, and this tool gives up resolution rather than quality, because a small sharp picture is more useful than a full sized smeared one. Flat artwork behaves completely differently. A scanned signature is mostly white with a few thousand dark pixels, and JPEG spends almost nothing on flat areas, so a 600 by 200 signature commonly lands at 8 to 15 KB with no downscaling at all. The tool works by measuring rather than guessing. It encodes once, reads the exact byte count and pixel count of what came out, computes the bytes per pixel that this specific image actually costs, and solves for the pixel count that would fit the budget. That solved size drives the next attempt. Two or three rounds is normally enough. There are hard stops in both directions: quality never drops below about 0.54 on the JPEG scale, the long side never goes below 96 pixels, and no more than five encodes ever run. When those limits are hit before 20 KB is, the page says so and reports the smallest file it did produce. Camera metadata is stripped, because an EXIF block alone can eat several kilobytes of a 20 KB allowance. Everything runs on the canvas element in your own browser; no file is uploaded anywhere.