There is the expected privacy-surrendering API in which you send all your URLs to Google, and a more defensible one in which you download some sort of database

There is the expected privacy-surrendering API in which you send all your URLs to Google, and a more defensible one in which you download some sort of database to then query locally: https://developers.google.com/safe-browsing/v4 https://developers.google.com/safe-browsing/v4