Comment by MichaelZuo

> Why not just "enter grainy distorted 123 + 456"? No JS, no tracking. It takes literally milliseconds to generate and present. I've seen this work on large scale. Why is it mandatory to run tons of JS anyway?

Probably because it takes fractions of a cent to solve those grainy distorted captchas?

Whereas its not so trivial to get an extra IP address, extra computer, etc.

I can’t think of any alternative that would still be as onerous a bar to spammers and bots but also be less restrictive for genuine users. Other then linking real IDs, which has its own can of worms.