X’s timeline crops a single image down to a wide preview no matter what shape you upload, so a tall or square photo often loses its top or bottom before anyone taps to expand it. Post something wide to begin with and you skip that crop entirely.
Here are the dimensions X actually uses.
| Type | Size | Aspect ratio |
|---|---|---|
| Profile Photo | 400 x 400 | 1:1 |
| Header / Banner | 1500 x 500 | 3:1 |
| In-Stream Photo | 1200 x 675 | 16:9 |
| Two Images | 700 x 800 | 7:8 |
| Card Image (Summary) | 800 x 418 | 1.91:1 |
| Card Image (Large) | 1200 x 628 | 1.91:1 |
| Ad (Single) | 1200 x 675 | 16:9 |
| Ad (Carousel) | 800 x 800 | 1:1 |
Which size to actually use
1200 x 675 is the working size for a standalone image post and the one worth defaulting to. It matches the 16:9 frame the timeline crops everything to, so what you upload is what people see, with no surprise cropping. A square image still posts fine, but it gets squeezed into that same wide frame and ends up looking smaller than a native 16:9 image next to it.
Posting exactly two images is the one case where the shape changes. X puts them side by side, so each one is displayed tall rather than wide, and 700 x 800 is the size built for that slot. Three or four images get divided again, so keep a multi-image set consistent rather than mixing ratios inside it.
Header photos get cropped differently on mobile and desktop, so keep any text or logo centered rather than near the edges, both versions will still show it.
Format and common mistakes
Export as JPEG for photos and PNG when you need transparency or crisp text over a background. Uploading a portrait photo shot on a phone and letting X crop it is the single most common mistake here, since the crop keeps the middle and loses whatever was framed at the top or bottom. A social media image resizer fixes that before you post, rather than after.
If you’re not sure how an image will actually crop, run it through an X image size checker first. And if you’re formatting across more than one platform at once, the social media image size guide keeps every dimension in one place instead of ten open tabs.
Watch file size too. X compresses large images on upload regardless, so a smaller, already-compressed file gives you more control over the result than a 12MB original. An image compressor handles that without a visible quality hit.