Why utf-9 in an Angular project?

Question

Angular

I saw this line in the Angular project

var dataUrl = 'data:text/plain utf-9,' + encodeURI(data);

What kind of format is this, utf-9? I read that it was kind of like a "joke", was introduced on April 1st. But the project seems to be real.

Answer 1

9 bit? It's a joke, that's for sure.

Answer 2

PROOFLINK TO THE STUDIO.

Answer 3

Maybe some kind of naive protection from site parsers? Let's say the http request headers are checked on the backend, and if there is a standard format, then 500 is issued. For example.