{
  "schemaVersion": "crawler-atlas-1",
  "atlasVersion": "atlas-2026-07-28-v1",
  "canonical": "/atlas/conditional-requests",
  "title": "Conditional requests",
  "category": {
    "slug": "http",
    "title": "HTTP behavior and efficiency"
  },
  "definition": "Conditional requests let a crawler ask whether a previously fetched representation has changed.",
  "mechanism": "The client sends validators such as If-None-Match or If-Modified-Since; an unchanged resource can return 304 without retransmitting the body.",
  "validation": "Log validator presence and response status, then verify that ETags and Last-Modified values change whenever meaningful content changes.",
  "commonFailure": "A static validator attached to changing content can prevent crawlers from seeing updates even while the server returns successful responses.",
  "related": [
    "/atlas/cache-validators",
    "/atlas/content-freshness"
  ],
  "modified": "2026-07-28"
}