If you are looking for a password, you can check to see if the password you want to use has ever been used. Just go to the Have I Been Pwned website and look at the Passwords link. They now have a list of the passwords that have been breached. You can test your password against it and it will tell you if it’s been breached but it will also tell you it may not be a good password even if it’s not been breached.
Here is what you get if your password has been used before and found on a breach list:
Here is what it looks like if it hasn’t: