| Requirement | Value |
|---|---|
| Pixel size | 256 × 64 |
| Target size | 5 – 20 KB |
| Format | JPEG only |
A signature is landscape — 256 pixels wide by 64 tall, four times wider than it is high. A photograph is portrait. Forcing a signature into a portrait frame stretches it, and that is the single most common reason it is rejected.
Sign on plain white paper with a black or dark blue pen. Pencil and light-coloured ink almost disappear once the image is compressed.
Because a signature is a simple image it compresses very easily and can fall below the 5 KB minimum that many portals enforce. This preset holds it between 5 and 20 KB.