Resolve conflicting robots.txt rules using RFC 9309's precedence order instead of assuming line order matters
domain: rfc-editor.org · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Group rules by matched user-agent record per RFC 9309, then evaluate only the single most specific matching group for a crawler - never merge multiple groups
Within that group, find the rule (Allow or Disallow) whose path pattern is the longest/most specific match for the target URL
When two rules of equal specificity conflict, apply Allow over Disallow per RFC 9309's tie-break
Treat the rule set as unordered - reordering Allow/Disallow lines should not change the outcome under a spec-compliant parser
Default to allowed when no rule in the matched group applies to the URL
Known gotchas
Some older or non-compliant crawlers still apply first-match or line-order logic instead of RFC 9309 longest-match - test against your actual target crawler, not just the spec
RFC 9309 caps parsing at the first 500 kibibytes of a robots.txt file; content beyond that is ignored
A matched user-agent group with no applicable rules means full allow, which can be a silent gotcha if you intended to block by omission
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