FilterLists vs Mozilla http scanner

FilterLists is Collin Barrett's independent, actively-maintained directory of filter and host lists used by adblockers, firewalls, and DNS sinkholes to block ads, trackers, malware, and other unwanted content. Its ASP.NET Core REST API serves the same catalog that powers the site -- filter lists, the domains/URLs they target, licenses, and maintainer info -- with an interactive Swagger UI for exploring the schema before writing a query. The API and site are fully free and keyless, open-sourced on GitHub with commits as recent as this week. The API lives entirely on a separate `api.filterlists.com` host -- the intuitive REST paths on the main `filterlists.com` domain just return the site's own SPA shell.

The HTTP Observatory grades a website's security headers -- CSP, HSTS, cookie flags, and more -- against Mozilla's recommended baseline, the same engine behind the long-running Mozilla Observatory scanner. The original mozilla/http-observatory Python API was shut down on 2024-10-31 when the tool moved to MDN; automated callers now POST to a v2 scan endpoint that returns a grade, score, and pass/fail counts, with a details link back to the full MDN report. It's fully public and keyless, rate-limited to one fresh scan per host per minute (cached results are returned for repeat calls within that window), and built for CI-pipeline use.