{
  "id": "w3c-validator-nu",
  "name": "Validator.nu (W3C Nu HTML Checker)",
  "operator": {
    "name": "World Wide Web Consortium (W3C)",
    "url": "https://www.w3.org"
  },
  "description": "The fetcher behind the Nu HTML Checker, the W3C validation service that checks a user-submitted URL against current HTML conformance rules. W3C's validation services page lists its user agent and states that all W3C validator traffic comes from one published IPv4 address and one IPv6 prefix.",
  "docs": [
    "https://validator.w3.org/services"
  ],
  "category": "seo",
  "user_agents": {
    "patterns": [
      "Validator\\.nu/"
    ],
    "instances": [
      "Validator.nu/LV"
    ]
  },
  "behavior": {
    "respects_robots_txt": false
  },
  "verification": [
    {
      "type": "static_cidrs",
      "cidrs": [
        "52.22.66.203/32",
        "2600:1f18:7d7a:2700::/56"
      ]
    }
  ],
  "tier": 2,
  "tier_label": "Verifiable",
  "first_seen": "2026-09-01T13:17:25.816Z",
  "resolved_cidrs": [
    "2600:1f18:7d7a:2700::/56",
    "52.22.66.203/32"
  ]
}