Check if Password was Leaked in a Data Breach
Audit your password security using the industry-standard k-anonymity HIBP protocol. 100% private: your password or full hash never leaves your phone.
Password Breach Checker
Your password is hashed with SHA-1 on your phone. Only the first 5 characters of the hash are checked against public breach archives. Your actual password remains 100% secret.
How to check if password was leaked in a data breach in 3 simple steps
Enter password securely
Type or paste your password into the protected client-side input field.
Generate 5-char hash prefix
The browser computes SHA-1 and sends only the first 5 characters for k-anonymity.
Inspect breach result
Instantly see if your password matches any compromised credential leak records.
Frequently Asked Questions
How does k-anonymity protect my password?
Only the first 5 characters of your password's SHA-1 hash are sent to the API. Thousands of matching hashes are returned, and your browser matches the rest locally.
Does alreadytaken.me store my password?
Never. Neither our servers nor any third party ever receives your password or complete hash.
What should I do if my password is found in a breach?
Immediately change that password on any account where it was used, and enable two-factor authentication (2FA).
Can I test passwords while disconnected from the web?
The 5-character prefix lookup requires a brief network query to fetch the anonymous suffix pool from Have I Been Pwned.
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