How to make a background blur in CSS with one line of code

Background blurs are cool. This is an undisputed fact. Every single user interface should have at least ten background blurs in them (preferably stacked on top of each other), and every interface made since the creation of the world wide web without background blurs should be flagged as high priority technical debt. This is the Truth. Developers love when you show them design proofs with background blurs. This is false.

That’s because background blurs have been basically impossible to implement on web applications, making designers feel frustrated, lied to, and utterly useless as human beings. But that all changes today…