I obtain the SHA1 hashes published by HIBP, load them into a bloom filter and use that for checks. It's super fast (constant time lookups) and avoids a network

I obtain the SHA1 hashes published by HIBP, load them into a bloom filter and use that for checks. It's super fast (constant time lookups) and avoids a network dependency/third party service. Here's working Go code: https://github.com/w8rbt/bp https://github.com/w8rbt/bp Edit: This is solely for password vetting during account creation and password reset (which will remain free/no-cost in the API).