Make a tweet image with a transparent background

If you are placing a tweet into a video thumbnail, a slide or a design mockup, a white rectangle around it ruins the composition. A transparent export gives you just the card, with a real alpha channel, so it sits on whatever is behind it.

Paste a link above to see the preview here.

This page opens with the background set to transparent and PNG selected, since PNG and WebP are the only common formats with alpha. You can also make the card itself transparent and keep only the text, which is useful for overlaying a tweet quote onto footage.

Questions

Which formats keep a transparent background?
PNG and WebP. JPEG has no alpha channel, so exporting as JPG flattens transparency to a solid colour.
Why does my transparent image have a black background?
It was almost certainly saved as JPG, or opened in an app that shows alpha as black. Re-export as PNG and check in a browser.
Can the tweet card itself be transparent, not just the surround?
Yes. Setting the card background to transparent leaves only the avatar, name and text, which works well over video.