UPDATE – there is a new image header size for Twitter in 2014, and, as the below post is still very popular, it remains, but note this is no longer the case (though images in this size should still look quite good).
The New Twitter Header Image Dimensions
New for 2014, the header image size is: 1500 x 500 in pixels.
This is for the new Twitter profiles that rolled out a month or two ago (correct June 2014).
The below information is no longer accurate, but remains as a historical archive of the old information, and there are also some somewhat helpful comments at the bottom (scroll down).
As we wrote a post about Facebook Cover Image Size, just now, and we also today completed a Twitter Header Image re-working for Race-Calendar.com, it makes sense to also post a quick item which explains the Twitter header image dimensions, too.
Twitter Header Image Size / Dimensions
520px x 260px
That is, 520 pixels by 260 pixels.
You can use .JPG, .GIF or .PNG, though we find that GIF images tend to upload more easily (sometimes tricky uploading PNG files, for some reason) and that gif can be compressed to a smaller file size.[UPDATE] please note that these image dimensions are different from those suggested by Twitter itself, even, but look and work as intended, and upload more easily than the larger dimension images which often fail to upload at Twitter. Twitter’s suggested header image size is 1252×626. Importantly, note that the aspect ratio of our image size and Twitters is exactly the same: ours is the smallest possible size, great for image optimization: why go bigger when it won’t display in that size?[/UPDATE]
Where is the Twitter Header Image Displayed?
The Twitter header image is displayed on your Twitter home page, i.e. if someone clicks on your Twitter name. For example, for Race-Calendar.com, it is here.
Best Styling for Twitter Header Images
Because the Twitter header image contains your Twitter logo in a square in the centre, and your Twitter bio, username, and web address in white text below that in the centre, too, it is best if you don’t have too much “going on” front and centre of your header image. A landscape, for example, would work well.
As an example of what you might like to do with your Twitter header, for Race-Calendar.com, we used a broad running scene, but found that the words were a little “lost” so on the second iteration, we put dark grey boxes where the Twitter words were to go, to make the text more readable. See the example in the below screenshot:
If you have any questions or comments, please leave them below. If you’d like us to design or manage your corporate Twitter or Facebook account, please feel free to contact us any time.