The site, haveibeenpwned.com, allowed visitors to enter their email address to learn if it is in one of several publicly released databases of breached email addresses, with a total of 154 million email addresses.
The site has been widely used, but the number one request of users has been for an automatic notification service, site founder Troy Hunt told ZDNet.
The notification service has now been added to the site, Hunt said.
In addition to a one-time check, visitors can click on "Notify me if my address gets pwned in the future," and they will be registered for notifications.
The haveibeenpwned.com site is a free service.