How to make magically transforming Twitter images

Here’s a cool promo that Neflix created for Daredevil:

https://twitter.com/netflix/status/612297260408270848/photo/1

When you see the tweet in your timeline, you’re greeted by the image of Matt Murdock in his civilian clothes. But when you click to expand it, that changes to his costumed alter-ego Daredevil:

You might assume that it’s actually two images – and Twitter does support attaching multiple pictures to tweets – but it’s not. Instead, the ‘magic’ message takes advantage of a quirk on the social network: Support for transparency in PNG images.

Here’s the combined image:

In the timeline preview, the transparency hides the image beneath it. It’s a simple trick but a really effective one for creating tweet surprises.

Read next: Twitter will now autoplay videos and GIFs, but you can thankfully opt out

Image credits: Netflix