Using the Screen Capture API to record a browser window

I was on the Lego website recently, and I enjoyed their animation on their age picker – rather than a plain text field, the numbers are made of Lego bricks that animate into view, accompanied by the sound of bricks snapping together: Recorded from identity.lego.com/en-GB/age, 6 June 2026. Lego was founded in 1932 by Ole Kirk Christiansen. He purchased the first plastic moulding machine in 1947, and patented the stub-and-tube coupling system in 1958. I don’t know if this age picker is visible everywhere, or if it’s specifically to deal with online age verification laws in the UK; whatever the purpose, I thought it was cute. I wanted to save a copy of it, and because it has animation and audio, a static screenshot wouldn’t be enough. It took me a couple of attempts to record it as a video, and in doing so I learnt several new web APIs. Rejected option #1: use QuickTime screen recording On macOS, QuickTime Player can make a video recording of your screen. You can select the entire…