Password Leak Checker

A Password Leak Checker lets you check whether a password has appeared in known data breaches — without ever sending your actual password over the internet. This tool uses the k-anonymity model from Have I Been Pwned (HIBP) by Troy Hunt, a free service that aggregates and verifies data from publicly disclosed breaches containing billions of compromised accounts.

Here is how it preserves your privacy:

1. Your password is hashed using SHA-1 in your browser
2. Only the first 5 characters of the hash are sent to the HIBP API
3. The API returns all hash suffixes that match those 5 characters
4. Your browser checks if your full hash is in the returned list
5. If found, the count of how many times it appeared is displayed

Your password never leaves your browser. Only a partial hash prefix is sent, making it impossible to reconstruct the original password.

Common use cases include checking if your current passwords have been compromised, verifying new passwords before using them, and educating users about password security.

1. Type your password — Enter the password you want to check in the input field. The input is masked for security.
2. Click Check for Leaks — Press the button to start the secure check. A spinner indicates the lookup is in progress.
3. Review the result — If the password is not found, a green message confirms it's safe. If found, a red warning shows how many times it appeared in breaches.
4. Take action if needed — If your password was leaked, change it immediately on any accounts where you use it.