Have I Been Pwned is a free, comprehensive security resource that allows individuals to check if their email addresses or passwords have been exposed in known data breaches. Created by Troy Hunt in 2013, the service helps users assess their personal security risks in the wake of widespread online account compromises. The platform aggregates data from thousands of breaches, providing a centralized repository that informs users which of their accounts have been affected, what specific data types were leaked, and when the incidents occurred.

Beyond simple email lookups, the platform provides proactive security monitoring through an email notification system and a robust API for developers. The service includes specialized features like Pwned Passwords, which uses a secure k-anonymity model to check if passwords have appeared in leaked datasets without ever exposing the password itself to the service. Organizations can also use domain search capabilities to audit their own exposure, track breaches across their registered domains, and monitor for credentials captured by info-stealing malware (stealer logs).

Some of the key features are:

• Email Breach Search: Quickly identify which data breaches contain your email address and what information was exposed.
• Pwned Passwords: Verify if a password has appeared in historical data breaches using a privacy-preserving k-anonymity mechanism.
• Breach Notifications: Subscribe to receive alerts whenever your email address appears in newly discovered data breaches.
• Domain Monitoring: Verify domain control to track leaked credentials across an entire organization's email footprint.
• Stealer Log Detection: Identify credentials compromised by info-stealing malware captured in public logs.
• RESTful API: Integrate HIBP services into custom applications with an API supporting breach metadata, password checking, and domain management.
• MCP Server Support: Provide Model Context Protocol access to breach metadata, logs, and password checks for AI agents and conversational interfaces.
• Privacy-First Design: Utilize k-anonymity for password and email searches to ensure sensitive credentials are never fully transmitted to the platform.

To use the service, simply enter an email address on the main website to receive a summary of its presence in recorded breaches. For more advanced features, such as domain-wide monitoring or programmatically checking for compromises, users can access the dashboard to manage keys and subscriptions. The service relies on security research and publicly available data to maintain its repository, constantly updating to reflect the evolving threat landscape.

Some common use cases include:

• Personal Security Auditing: Individuals can use the site to understand which of their online accounts require immediate password changes or enhanced security measures.
• Credential Stuffing Defense: Developers can integrate the Pwned Passwords API to prevent users from choosing weak or already-compromised passwords during account creation.
• Enterprise Breach Management: Organizations can monitor their corporate domain to identify and remediate compromised accounts held by their employees.
• MSP Security Services: Managed Service Providers can use the domain search and API features to monitor their customers' security posture across large portfolios of domains.
• AI Agent Security Integration: AI-driven applications can use the MCP server to provide real-time security context regarding breach status to users in a conversation.