What matters
X Header Image dimensions at a glance
The X header is a long, shallow 3:1 canvas that sits behind the profile avatar and bio. It works best with one focal idea and broad horizontal composition.
The header is the largest visual element on your profile. A clean, correctly sized header makes the profile feel professional; a stretched or cropped one undermines credibility.
Wrong-ratio headers get cropped awkwardly, especially when the avatar overlaps key parts of the design. Mobile crops more aggressively than desktop.