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Get Started Free →Use when applies to any site with a dynamically generated or manually maintained XML sitemap. Use when investigating crawl errors or after a site migration that removed pages.
.claude/skills/thedaviddias-sitemap-4xx/SKILL.md| Test case | Without → With | Effect | Δ tokens | Δ turns |
|---|---|---|---|---|
| case-13 | ✗→✓ | ▲ Improved | 3% | 0% |
| case-17 | ✓→✗ | ▼ Worse | -14% | 0% |
| case-02 | ✓→✓ | ＝ Same ✓ | -10% | 0% |
| case-03 | ✓→✓ | ＝ Same ✓ | 16% | 0% |
| case-04 | ✓→✓ | ＝ Same ✓ | -7% | 0% |
Including 4XX URLs in a sitemap signals poor site maintenance to Google, wastes crawl budget on non-existent pages, and generates errors in Search Console that can mask real indexing issues.
Fetch all URLs listed in the sitemap and record their HTTP status codes. Flag any URL returning 4XX (404 Not Found, 410 Gone, 403 Forbidden). Cross-reference against Google Search Console → Coverage for corroborating data.
For each 4XX URL: if the content moved, set up a 301 redirect to the new URL and add the new URL to the sitemap. If the content is permanently gone, return 410 Gone and remove the URL from the sitemap. Regenerate and resubmit the sitemap.
Explain why sitemaps must only contain live, indexable URLs, how 4XX URLs in sitemaps affect crawl budget allocation, and the difference between 404 and 410 status codes for deindexing.
Review metadata generation, rendered HTML, structured data, and response headers related to 4XX Pages in Sitemap. Flag exact routes or templates where search-facing output violates the rule, and describe how to verify the final page output.
For full implementation details, code examples, and framework-specific guidance, see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/seo/sitemap-4xx
| Case | Status | Duration (ms) | Turns | Tokens | Tool calls | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Without | With | Δ | Without | With | Δ | Without | With | Δ | Without | With | Δ | ||
case-02 | pass→pass | 11,567 | 8,018 | -31% | 1 | 1 | 0% | 2,063 | 1,864 | -10% | 0 | 0 | — |
case-03 | pass→pass | 12,007 | 10,603 | -12% | 1 | 1 | 0% | 2,015 | 2,334 | +16% | 0 | 0 | — |
case-04 | pass→pass | 9,834 | 7,495 | -24% | 1 | 1 | 0% | 1,814 | 1,678 | -7% | 0 | 0 | — |
case-01 | fail→fail | 16,664 | 12,288 | -26% | 1 | 1 | 0% | 3,170 | 2,875 | -9% | 0 | 0 | — |
case-05 | pass→pass | 10,383 | 11,025 | +6% | 1 | 1 | 0% | 1,827 | 2,426 | +33% | 0 | 0 | — |
case-06 | pass→pass | 14,874 | 12,114 | -19% | 1 | 1 | 0% | 2,622 | 2,774 | +6% | 0 | 0 | — |
case-07 | fail→fail | 12,271 | 11,892 | -3% | 1 | 1 | 0% | 2,198 | 2,532 | +15% | 0 | 0 | — |
case-08 | pass→pass | 10,417 | 11,847 | +14% | 1 | 1 | 0% | 1,875 | 2,578 | +37% | 0 | 0 | — |
case-09 | pass→pass | 10,398 | 8,365 | -20% | 1 | 1 | 0% | 2,215 | 2,054 | -7% | 0 | 0 | — |
case-10 | pass→pass | 15,367 | 14,528 | -5% | 1 | 1 | 0% | 2,542 | 2,981 | +17% | 0 | 0 | — |
case-11 | pass→pass | 10,737 | 7,478 | -30% | 1 | 1 | 0% | 1,924 | 1,786 | -7% | 0 | 0 | — |
case-12 | pass→pass | 11,913 | 6,291 | -47% | 1 | 1 | 0% | 2,122 | 1,589 | -25% | 0 | 0 | — |
case-13 | fail→pass | 11,887 | 9,974 | -16% | 1 | 1 | 0% | 2,068 | 2,130 | +3% | 0 | 0 | — |
case-14 | pass→pass | 16,849 | 12,915 | -23% | 1 | 1 | 0% | 3,002 | 2,756 | -8% | 0 | 0 | — |
case-15 | pass→pass | 8,905 | 5,939 | -33% | 1 | 1 | 0% | 1,627 | 1,500 | -8% | 0 | 0 | — |
case-16 | fail→fail | 13,667 | 9,478 | -31% | 1 | 1 | 0% | 2,266 | 1,985 | -12% | 0 | 0 | — |
case-17 | pass→fail | 8,386 | 4,880 | -42% | 1 | 1 | 0% | 1,537 | 1,325 | -14% | 0 | 0 | — |
case-18 | pass→pass | 10,934 | 9,783 | -11% | 1 | 1 | 0% | 1,997 | 2,142 | +7% | 0 | 0 | — |
case-19 | pass→pass | 7,997 | 8,927 | +12% | 1 | 1 | 0% | 1,651 | 2,161 | +31% | 0 | 0 | — |
case-20 | pass→pass | 10,574 | 7,403 | -30% | 1 | 1 | 0% | 1,773 | 1,754 | -1% | 0 | 0 | — |
case-21 | pass→pass | 14,837 | 11,721 | -21% | 1 | 1 | 0% | 2,598 | 2,591 | -0% | 0 | 0 | — |
case-22 | pass→pass | 12,462 | 10,244 | -18% | 1 | 1 | 0% | 2,262 | 2,367 | +5% | 0 | 0 | — |
case-23 | pass→pass | 14,006 | 12,185 | -13% | 1 | 1 | 0% | 2,713 | 2,821 | +4% | 0 | 0 | — |
DecimalAI ran this skill against gemini-3.6-flash twice over the same eval suite — once with the skill loaded and once without — and compared the two runs case by case. 23 cases were attempted. The headline lift of 0 percentage points is the difference between those two pass rates over the 23 comparable cases. 1 case got worse with the skill loaded, and it is included in that figure.
Without the skill loaded, the model failed this case. With it loaded, the same prompt on the same model passed. This is one improved case from the latest verified run; every case, including any that regressed, is in the table above.
Other measured skills in the registry, with their headline benchmark lift.