I love diagrams.net, it's what I use whenever I need to prototype a UI. And one thing I particularly love is you don't need to register to use it or to save you

I love diagrams.net, it's what I use whenever I need to prototype a UI. And one thing I particularly love is you don't need to register to use it or to save your work. Most online tools have a dark pattern where they pretend it's possible to use without registering, they even say so on their landing page, and then when you go to save your work they force you to register. Diagrams.net doesn't do that and they have my respect.