If you have ever signed up for an online account, some of those login details have probably leaked. Companies get hacked, databases get copied, and the stolen files get traded or dumped for years. An email breach check tells you whether your address or password is in a known leak. If it is, the rest of this page is the order of operations: check, rotate, lock down 2FA, then keep checking.
What a data breach actually is
A data breach happens when information held by a company or website is stolen or leaked. That information often includes email addresses and passwords, but it can also contain phone numbers, usernames, home addresses, and other personal details. Sometimes the breach comes from a direct attack on a company's servers. Other times an employee makes a mistake that leaves a database open to the public.
Once that data is out, it does not disappear. It gets collected, combined with other leaks, and circulated for years. A password you used in 2016 can still be sitting in a file that someone downloads today.
How to do a data breach lookup
Paste the address into a checker that searches collected leak data. Revealer's data breach lookup checks 800+ platforms and known breach datasets, which is how it catches leaks the smaller checkers skip.
A useful result tells you more than a yes or no. It shows which breaches your email appeared in and what type of data was exposed in each one. That matters, because an email leaked alongside a password is a bigger problem than an email leaked on its own. If a result shows a password next to your email, treat that password as public. Stop using it anywhere, including on sites that were not in the leak.
The same lookup covers more than classic company breaches. Passwords also surface in stealer logs captured by malware on infected devices, and you can check any address you own with a plain email lookup to see everywhere it is exposed.
It is worth checking every email address you use, including old ones. People often forget about accounts they set up years ago, and those forgotten accounts are exactly the ones that tend to use weak or reused passwords.
Credential stuffing: why leaked credentials are dangerous
The damage is credential stuffing, not the original leak. Attackers know that most people reuse the same password across many sites. So when they get a working email and password from one breach, they do not just try it on that one site. They use automated tools to test that same combination against banks, email providers, shopping sites, and social media accounts, all at once.
If you used the same password for your email and your online banking, a leak from an unrelated forum can hand an attacker the keys to both. This is why a single old breach can lead to accounts being taken over months or years later. The attacker is not guessing your password. They already have it, and they are simply trying it everywhere.
Email accounts are a favorite target because they act as a master key. If someone controls your email, they can reset the password on almost any other account by clicking "forgot password" and intercepting the reset link.
What to do if your email was exposed
A match is not an emergency. It is a to-do list. Work through these in order.
Change the password on the affected account first, then change it anywhere else you used the same or a similar password. Do this first. Until the reused password is gone, stuffing still works. Use a unique password for every account so that one leak can never spread.
Because no one can remember dozens of unique passwords, use a password manager. It generates and stores strong passwords for you, so the only password you need to remember is the one for the manager itself.
Turn on two-factor authentication, often shown as 2FA, on any account that offers it. This means that even if someone has your password, they also need a code from your phone or an authenticator app to get in. Enable it on your email and banking accounts before anything else.
Watch for warning signs. Be cautious of emails claiming to be from a company that was breached, since attackers often follow up leaks with phishing messages aimed at the exact people who were exposed. Check your account activity and login history where available, and set up alerts for new sign-ins.
Check again. New dumps land all the time, and an address that is clean in May can show up in June. A five-minute check every month beats finding out after someone is already in the mailbox.
Frequently asked questions
How do I check if my email was in a data breach?
Enter your address into an email breach check that searches collected leak data and reports which breaches it appears in. Revealer's data breach lookup checks your email against 800+ platforms and known breach datasets, so it can surface leaks smaller checkers miss, and it shows what type of data was exposed in each one.
Was my password leaked, or just my email?
A good breach check answers both. It tells you whether your email appeared and whether a password was exposed alongside it. If a result shows a leaked password, treat it as public and change it everywhere you used it. Plaintext passwords also turn up in stealer logs, which a full data breach lookup searches too.
What is credential stuffing?
Credential stuffing is when attackers take a working email-and-password pair from one leak and use automated tools to try it against banks, email providers, and other sites at once. Because so many people reuse passwords, one old breach can compromise several accounts. A unique password per account is what shuts credential stuffing down.
Is a free email breach check accurate?
Accuracy depends on how much breach data the tool searches. A checker tied to a small dataset will miss leaks, while a data breach lookup built on a large collection of known breach datasets covers far more ground. Revealer's check is free to run and reports the specific breaches your email or password appears in, not just a yes-or-no.
How often should I run a breach check?
New dumps land constantly, so an address that is clean today may appear in a leak next month. A quick periodic email breach check is cheaper than reacting after an account is already gone.
If you want to see whether your own email or passwords have turned up in a known leak, run a free check with Revealer's data breach lookup and start securing any accounts that show up.