The Have I Been Pwned website lets you check your email address against a large number of data breaches. If it’s in there, then your email address and probably some form of your password are out there to the public, all ready for nefarious use.
And security researchers all say that you shouldn’t re-use passwords, because that’s unsafe precisely because of these data breaches. Wouldn’t it be nice to be warned that your email address or username has been compromised, and then you’d get some kind of warning to not re-use a password? The ideal time for this is when you’re picking a new password for your account, right?
If the site you’re logging in to is built with AngularJS then I have the thing for you! Well, for whoever built the website, at least:
It’s a simple AngularJS directive that checks against the HIBP database!
I’ve put up a very simple example of it here for you to try out as an end-user.