Have I Been Pwned (HIBP) is a free data breach search and notification service. The service has been used by tens of millions of people to search through billions of breached records and supports tens of thousands of visitors a day. HIBP aggregates data that's been exposed publicly and enables individuals and organisations to assess their exposure. Searches only require an email address and provide immediate feedback. The notification service monitors for ongoing exposure and emails an address owner if it subsequently turns up in a data breach. HIBP also supports free domain searches for organisations to assess the total exposure of addresses on corporate domains. As with email addresses, domain searches can be performed on the spot and notifications sent if future exposure is detected. There is also a freely accessible API that enables developers to build solutions to help victims of data breaches understand their exposure.