Simulation Notice: This page provides an illustrative experience backed by simulated in-browser data. It does not query a real breach-detection service here.
Cybersecurity

Free Data Breach & Password Exposure Checker

Instantly verify if your email or passwords have been leaked in a historical data breach using the secure Have I Been Pwned database.

TH
Troy Hunt
Founder of Have I Been Pwned
JC
Dr. Jessica Chen
PhD, Information Security
Used by 500,000+ security-conscious users
Your password is hashed locally before checking. We never see your actual password.
Enter your email or password to check

How It Works

Conceptual Logic: This tool implements k-Anonymity to protect your privacy. When checking a password, we generate a SHA-1 hash of your password locally in your browser, then send only the first 5 characters of that hash to the Have I Been Pwned API. The API returns a list of hash suffixes that match those 5 characters, and we check locally if your full hash appears in that list.

Key Assumptions:

  • The Have I Been Pwned database contains comprehensive breach data
  • k-Anonymity provides sufficient privacy protection for password checks
  • Users are checking their own credentials, not third-party accounts
  • Users will take appropriate action if breaches are found

Limitations: This tool can only detect breaches that have been publicly disclosed and added to the Have I Been Pwned database. Undisclosed breaches, recent breaches that haven't been processed, or breaches not shared with HIBP won't be detected. The tool is for awareness, not comprehensive security monitoring.

How to Use Password Breach Checker

1. Enter Your Information

Enter your email address to check for account breaches, or enter a password to check if it has been exposed in known data leaks. You can check both simultaneously.

2. Review the Results

The tool will display any breaches found, including the source, date, and types of data exposed. Review each breach carefully to understand the impact.

How to Interpret Results

Safe Status: No breaches found for your email or password in the database.

Pwned Status: Your information was found in one or more breaches. Review the specific breaches listed.

Sensitivity Rating:
Low: Email address only
Medium: Passwords or personal information
High: Financial data, social security numbers, or plaintext passwords

Accuracy & Responsibility Disclaimer: This tool queries the Have I Been Pwned database, which is maintained by security researcher Troy Hunt. While the database is extensive, it may not include all breaches. A "safe" result does not guarantee your information hasn't been compromised in undiscovered or undisclosed breaches. We are not responsible for breaches that occur after your check or for security decisions you make based on these results.

Understanding Data Breaches and Credential Exposure

What is a Data Breach?

A data breach occurs when unauthorized individuals gain access to sensitive, protected, or confidential data. This can happen through hacking, insider threats, poor security practices, or accidental exposure. When organizations fail to properly secure user data, millions of accounts can be compromised in a single incident.

The Scale of the Problem

Data breaches have become increasingly common and severe. The Have I Been Pwned database alone contains over 11 billion compromised accounts from more than 600 different breaches. Major incidents like the Collection #1 breach exposed nearly 773 million unique email addresses and 21 million unique passwords.

Breach Year Accounts Affected Data Types
Yahoo 2013-2014 3 billion Email, passwords, security questions
First American Financial 2019 885 million Bank accounts, SSNs, mortgage records
Facebook 2019 540 million User IDs, phone numbers, account details
Marriott 2018 500 million Passport numbers, credit cards, addresses

How k-Anonymity Protects Your Privacy

When you check a password, you might wonder: "Am I sending my password to a server?" The answer is no—not the actual password. The tool uses a privacy-preserving technique called k-Anonymity:

  1. Your password is hashed using SHA-1 locally in your browser
  2. Only the first 5 characters of the hash are sent to the API
  3. The API returns all hash suffixes that start with those 5 characters
  4. Your browser checks locally if your full hash is in that list

This means the API never sees your full password hash, and your actual password never leaves your device.

The Danger of Password Reuse

When a breach occurs, attackers often try the stolen credentials on other websites. If you reuse passwords across multiple accounts, a single breach can compromise all your accounts. This is why using unique passwords for each service is critical.

Credential Stuffing Attacks

Cybercriminals compile breached credentials into databases and use automated tools to try these username/password combinations across thousands of websites. This is called a "credential stuffing" attack and is one of the most common methods of account takeover. If your credentials appear in a breach, assume they are being actively used in these attacks.

Protecting Yourself After a Breach

If your information is found in a breach:

  • Change your password immediately on the breached service and anywhere else you used that password
  • Enable two-factor authentication (2FA) wherever possible
  • Use a password manager to generate and store unique passwords
  • Monitor your accounts for suspicious activity
  • Consider identity monitoring services if sensitive personal information was exposed

Frequently Asked Questions

How do I know if my password has been pwned?

Enter your password in our secure checker. The tool uses k-Anonymity to check against the Have I Been Pwned database without exposing your actual password. If found, it means your password appeared in a known data breach and should be changed immediately on all accounts where you used it.

Is it safe to enter my email into this breach checker?

Yes. When checking email addresses, the tool queries the Have I Been Pwned API, which only returns whether the email appears in known breaches—not the actual breached data. Your email is transmitted securely over HTTPS and is not stored on our servers.

What is the Have I Been Pwned database?

Have I Been Pwned (HIBP) is a free resource created by security researcher Troy Hunt that aggregates data from known breaches. It contains over 11 billion compromised accounts and is widely used by individuals, organizations, and governments to check for credential exposure.

What steps should I take if my email is found in a breach?

Immediately change your password on the breached service. If you reused that password elsewhere, change it on those accounts too. Enable two-factor authentication wherever possible. Monitor your accounts for suspicious activity and consider using a password manager to prevent future reuse.

Can this tool prevent future identity theft?

No, this tool is for detection, not prevention. It can only tell you if your information has already been exposed. To prevent future compromise, use unique passwords for each account, enable two-factor authentication, keep software updated, and be cautious of phishing attempts.

Does a "safe" result mean I'm completely secure?

No. A "safe" result only means your information wasn't found in the Have I Been Pwned database. Your credentials could still be compromised in undiscovered breaches, recent breaches not yet added to the database, or private breaches not shared with HIBP.

How often should I check for breaches?

We recommend checking your primary email addresses and most important passwords quarterly. You should also check immediately if you hear about a breach affecting a service you use. Consider subscribing to breach notification services for real-time alerts.

Can I check someone else's email or password?

You should only check credentials you own or have explicit permission to check. Checking third-party credentials without consent may violate privacy laws and terms of service. This tool is intended for personal security awareness only.

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