X (Twitter) Image Size Guide

A header is 1500 by 500, and knowing that is not enough to make one that works, because two things sit on top of it that no size table mentions.

The first is the avatar. On the web profile it is a circle about 134 pixels across, near the left edge, hanging roughly half below the bottom of the header. Whatever you put in the bottom-left corner is behind it. This is what happens to the logo people centre vertically and align left out of habit: it renders perfectly in the export and is covered on the profile.

The second is the phone. The app shows the header in a shallower box than the 3:1 you uploaded, so it scales the image to fill the width and trims the sides, losing roughly a third of the width overall. A tagline that reaches comfortably across the canvas is cut off at both ends on the device most of your visitors are using.

Which gives one rule that survives both: everything that has to be read belongs in the middle band, horizontally centred and kept clear of the bottom-left. Upload your header above and the tool draws the avatar circle and the mobile trim lines straight onto it, which takes about four seconds and is the only way to be sure.

X re-encodes every image you upload. That is not the problem on its own, and it is not something you can turn off. The problem is what happens before the re-encode: if the dimensions do not match the placement, the image is resampled first, and a resample followed by a compression pass loses noticeably more than a compression pass alone. Text and flat colour show it first, which is why a screenshot of code looks worse on X than a photograph does.

So export at the exact numbers in the table. Not close to them, at them. If the graphic is mostly text or flat colour, export it as a PNG, where flat areas stay flat. If it is a photograph, export a JPG at high quality, because a PNG of a photograph is a large file that gets re-encoded to a JPG at the far end anyway, and the round trip costs you more than it saves. Either way, stay under 5MB, where the ceiling is, rather than right up against it.

The one case for doubling the dimensions is a graphic that has to stay crisp on a high-density screen and will be viewed large. Export it at twice the placement size and let the browser downscale once, which looks better than an upscale in either direction. Below the placement size there is nothing to be done: pixels that were never there cannot be recovered, and the tool above says so plainly when your image is too small rather than quietly stretching it.

The feed has opinions. A single attached image renders at 16:9 and anything you upload is cropped toward it, so 1600 by 900 is the shape that arrives intact. 4:5, at 1200 by 1500, is the tallest shape the timeline shows whole, and it is worth using deliberately: it occupies more vertical space in the feed than a landscape image does, which is most of why it performs.

Square is the safe default for a post with more than one image. Two to 4 images are arranged in a grid and each one is cropped again to fit its cell, so anything near an edge is at risk and the subject belongs in the middle. The link preview card is its own case: 1200 by 628 for the large one, which is the 2:1 shape that link previews use almost everywhere else, so one export usually serves every platform at once.

If you are mocking up any of this rather than shipping it, the post preview renders an image in the slot a real post gives it, and the character counter confirms the caption fits. One note on mockups generally: X’s interface font is Chirp and it is licensed for X’s own use rather than for third parties, so an honest mockup substitutes a system font rather than shipping the real one. bbuddy is not affiliated with or endorsed by X Corp, and these numbers are published by X and reproduced here as reference.