Where 10 KB limits come from
A 10 KB limit is about as small as upload fields get. You'll mostly see it for scanned signatures on online application forms, such as those for exams, recruitment drives, scholarships and some official registrations, where the system stores thousands of signatures and keeps each one tiny. Some forms also use very small limits for a thumbnail or a left-thumb impression.
At 10 KB there isn't room for a full-size phone photo. The image has to be small in pixels as well as heavily compressed. That's why ConvertirDocs doesn't only lower the quality: if the best quality that fits isn't enough, it also reduces the dimensions step by step until the file gets under the target.
Preparing a signature that stays readable
Sign with a dark pen, ideally black or blue, on plain white paper. Photograph it in daylight without shadows, holding the phone straight above the page. Then crop tightly around the signature with “Crop image”, so the file doesn't waste kilobytes on blank paper. A tight crop is the single most effective step: a small rectangle of ink compresses far better than a whole sheet.
After that, run it through this page. JPG is usually the most efficient format for a photographed signature. If the form gives exact pixel dimensions, set them first with “Resize image”, so you control the shape rather than leaving it to the automatic size reduction.
What happens when 10 KB isn't reachable
ConvertirDocs looks for the highest quality that fits under 10 KB. If it can't fit even at low quality, it shrinks the image in steps. If it still doesn't reach the target, you get the smallest version it achieved and a clear message saying the target wasn't met, so you never submit a file that's secretly too large.
In that case, crop tighter around the ink, photograph the signature again on whiter paper with better light, or check whether the form actually allows a little more, such as 20 KB. A form's own instructions are the only reliable source for its exact limits.
Signatures as part of a bigger application
Forms with a 10 KB signature field usually ask for a photo as well, often with a different limit. You can select both images at once here, but they'll share the same target. If the photo is allowed to be larger, process it separately on “Compress image to 20 KB” or “Compress image to 50 KB”, so it doesn't lose more quality than necessary. Keep the original files too: if the form rejects an upload, you can start again from the full-quality version instead of compressing an already compressed image.
Private and free
Signatures are sensitive. Your image is processed in your browser and isn't uploaded; nothing is stored. EXIF data, including GPS location, is removed from the result, and the camera's orientation is respected. There's no account, no daily limit and no watermark.