Some tools which help you to understand which category a URL is part of.
Is there a way to see why a URL has been blocked, and how the website has been catagorized? For example, facebook.com can be blocked because of the Core Blocked Content policy, but is there a test that shows more detail such as that Facebook is blocked for Social Media, Audio/Video or Unmoderated Hosting.
The first three involve actual content filtering:
1: Guardian > Quick links > Policy tester
2: Reports > Realtime > Web filter and hover over the entry in the policy field, which will then show you which policy was being picked up
3: Guardian > Block page > Block pages by enabling the three tick boxes that are highlighted in the attached screenshot
You will then see why a page has been blocked and if it is due to content filtering or due to a domain/URL being part of a category.
The fourth way does not involve content filtering and only checks if a domain/URL is part of a category
4: Guardian > Policy objects > Categories enter the domain/URL into the search field at the very top and you will see which categories a URL is part of.