How do you know if your credentials are compromised? Simple. Just go to Have I been pwned.com and fill in your email. This will tell you not only if your credentials are out on the street but also the breaches where it happened.

There is also a handy option to receive a notification when they find your email in any future breaches.

Wondering who else knows or uses the same password(s) as you do? Take a look at the Pwned Passwords and be surprised.