Breach Intelligence Radar

Password Breach Checker

Determine whether a credential exists in billions of leaked records from known corporate data breaches without exposing your plaintext password or full hash.

Analyzed locally · Never transmitted
0 characters

Breach Intelligence

k-Anonymity (5-char SHA-1 prefix)
Have I Been Pwned (HIBP) Radar

Check if this password has appeared in historical compromised credential datasets.

🔒 How Privacy is Preserved:

Your browser hashes the password locally into SHA-1. Only the first 5 characters (e.g., "5BAA6") are sent to HIBP. The server returns all matching suffix hashes, and your browser checks for matches locally.

Why Password Breach Intelligence is Critical

Many users believe that adding special characters to a password guarantees security. However, if that exact combination was previously exposed in a public leak (e.g. LinkedIn, Adobe, RockYou), automated attack bots test it in milliseconds using credential stuffing and rainbow tables.

How PassCheck Protects Your Privacy with K-Anonymity

When you enter a password into PassCheck:

  1. Your browser computes the 40-character SHA-1 hash locally in JavaScript.
  2. Only the first 5 characters (e.g. 5BAA6) are sent to the HIBP API.
  3. The API responds with all hash suffixes sharing those first 5 characters (hundreds of hashes).
  4. Your browser performs the final comparison locally to confirm if your exact suffix is present.