Securely check if your email / password was compromised in a breach

I've seen this extremely helpful site posted on HN & ignored in the past, so just want to say - despite the un-HN-worthy word "pwned" in the URL, this is a legitimate and reputable site, which more people should know about.

This computerphile video has more info: https://www.youtube.com/watch?v=hhUb5iknVJs