The X header is a short, wide strip
1500 across, 500 down
This pair is three times as wide as it is tall. In the social presets it is the X header, sometimes still called a Twitter header. It is not the X post, which is 1200 by 675, and it is not the X profile mark, which is a 400 square. A feed photo pasted into the header gets sliced into a ribbon. This page is for that ribbon. Type 1500 and 500 when the profile banner is the job, and build a different file for the post.
Put the subject in the middle band
Phones and desktops reveal different amounts of a header. The safest place for a face, a wordmark, or a product is the center. Edges disappear under the avatar, the name, and the buttons. Leave the corners quiet. If you have a landscape photo, crop it down to this short height on purpose so the eyes are not the part that gets cut. A square logo dropped in the middle of a plain field often reads more clearly than a busy photo.
Type the integers on one file
Enter 1500 as the width and 500 as the height. The resizer uses the first file you add. JPG, PNG, WebP, and GIF are accepted. The maximum edge is 10000 pixels, so this header is a modest shrink for a camera file. Enlarging a small banner up to 1500 wide does not invent detail. If the wordmark looks fuzzy, export again from a larger master. The resize runs on this device.
How the file is saved
JPEG and WebP can take a kilobyte target. Leave that box empty and they save at quality 0.92. PNG ignores the kilobyte target, which is the better path for a flat wordmark on a solid color. A photographic header is happier as JPEG. If the profile uploader also complains about weight, use the image compressor after the pixels are 1500 by 500. Do not switch to a taller size just to satisfy a kilobyte note.