- Class
- C2 Recommended
- Weight
- 4
- Severity on fail
- major
- Applies to
- Google and Bing
Test this rule on a live site with the XML sitemap checker. Free, no account needed.
Scope and evidence
Evaluated on each sitemap file with lastmod values. The book marks this requirement DOCUMENTED RECOMMENDATION.
Fail conditions
Each condition has a stable code and a reason template. The evaluator fills the placeholders from observed values only; no sentence in a report is generated.
future_lastmod{n} lastmod values in {sitemap} are later than the scan time, for example {example}. Google uses lastmod if it is consistently and verifiably accurate, and Bing uses it to prioritize recrawling.
The documented fix
Set lastmod from a stored "content last modified" timestamp, never from generation time or a scheduled date.
Sources, quoted
These are the passages the rule rests on, stored once in the knowledge base and emitted exactly as written. A citation marked for specific conditions appears only on findings with those codes.
“if it's consistently and verifiably (for example by comparing to the last modification of the page) accurate.”
[G-SITEMAP-BUILD] Build and submit a sitemap · XML sitemap · last updated 2026-07-08
https://developers.google.com/search/docs/crawling-indexing/sitemaps/build-sitemap“The lastmod field in your sitemap remains a key signal, helping Bing prioritize URLs for recrawling and reindexing, or skip them entirely if the content hasn't changed since the last crawl.”
[B-SITEMAP-2025] Keeping Content Discoverable with Sitemaps in AI Powered Search · Why lastmod Still Matters for AI Powered Indexing · last updated posted 2025-07-31
https://blogs.bing.com/webmaster/2025/7/Keeping-Content-Discoverable-with-Sitemaps-in-AI-Powered-Search/“the date must be set to the date the linked page was last modified, not when the sitemap is generated.”
[SITEMAPS-ORG] Sitemaps XML format (protocol) · XML tag definitions (lastmod) · last updated 2016-11-21
https://www.sitemaps.org/protocol.html