We provide a free test API key, which can be used to test the service's functionality against HIBP's integration test domain and email addresses on that domain. We do not provide free trials, sample data or API Keys for any use cases. The entry cost of a monthly HIBP subscription is based on the cost of a cup of coffee to ensure the cost doesn't prohibit legitimate use cases. You can start with a monthly subscription and cancel at any time if you wish to test the service before committing to an annual plan.
For groups of students interested in testing the API for a project or assignment, we recommend signing up with a shared email address accessible to all members. This allows you to share a single API key and split the cost among the group. Subscriptions can be taken on a month-to-month basis and cancelled at any time via the dashboard.