Pwned Passwords are more than half a billion passwords which have previously been exposed in data breaches. The service is detailed in the launch blog post then further expanded on with the release of version 2. The entire data set is both downloadable and searchable online via the Pwned Passwords page. It's also queryable via the following two APIs.
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Check If Your Passwords Have Been Pwned
February 17, 2019
5.0 and up