Check if a password has appeared in known data breaches using the k-anonymity Pwned Passwords API.
Every year, billions of credentials are exposed through data breaches, and those leaked username-password combinations are compiled into massive searchable databases that attackers actively use for credential-stuffing attacks. This Password Breach Checker lets you find out whether a specific password has ever appeared in one of these known breach collections, without ever exposing your actual password to any server.
This tool uses the Pwned Passwords API, maintained as part of the well-known Have I Been Pwned project, which aggregates hundreds of millions of passwords from real, documented data breaches. What makes this check genuinely privacy-respecting is a cryptographic technique called k-anonymity.
Instead of sending your password, or even its full hash, to the breach-check API, this tool first computes the SHA-1 hash of your password entirely inside your browser. It then sends only the first five characters of that hash to the API. The API responds with every known breached password hash sharing those same first five characters, along with how many times each has been seen in breaches. Your browser then compares the remaining part of your password's hash against that local list, entirely on your own device. The API operator never learns your actual password or your full hash.
If your password appears in the results, it means that exact password string has been recorded in at least one publicly known data breach, sometimes millions of times. This makes it unsafe to use anywhere, since automated attack tools have almost certainly already added it to their standard guessing lists.
A clean result means this exact password hasn't appeared in any indexed breach dataset yet. That's a good sign, but not a complete strength guarantee on its own. Combine this breach check with our Password Strength Checker for the full picture.
Unlike most other tools on this site, this one requires a live internet connection, since it queries a trusted third-party API directly from your browser.
Data breaches are disclosed continuously, sometimes years after they originally occurred, so a password that checked out clean six months ago could show up in this database today as new breach data gets indexed. Consider periodically re-checking your most important passwords, especially after hearing about a major breach affecting a service you use, and treat any positive match as an immediate, non-negotiable signal to rotate that password everywhere it has been reused.
If a breach check reveals a password match, it's also worth pausing to consider every other account where you might have used that same password, even with small variations. Attackers who obtain one leaked password commonly try close variations of it against other accounts too, so a comprehensive password audit after a positive match is more effective than simply changing the one account where you happened to test it here.
Consider also enabling breach-monitoring alerts through services that notify you automatically when your email address appears in a newly disclosed breach, complementing the manual, on-demand checks this tool provides for any specific password you want to test right now.
No. It sends only the first five characters of your password's SHA-1 hash, using a privacy-preserving technique called k-anonymity.
Stop using it immediately, especially if reused elsewhere. Generate a new, unique password with our Password Generator and update every account using the old one.
Not necessarily. Check it with our Password Strength Checker as well for a complete picture.
It queries a live third-party breach database to compare against known leaked credentials, requiring a real-time network request.
It's a widely respected service that has become a standard reference point across the security industry.
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