I don't know if there's any functional difference, but the obvious difference is that the SafeBrowsing API has volume limits in place which might affect you if

I don't know if there's any functional difference, but the obvious difference is that the SafeBrowsing API has volume limits in place which might affect you if you're running a high-ish volume service: If you use the Safe Browsing APIs (v4) to warn users about unsafe web resources, the following restrictions apply: Lookup API (v4): You can query up to 500 URLs in a single POST request. Lookup API (v4) and Update API (v4): A single API key can make requests for up to 10,000 clients per 24-hour period.