lastmod
A sitemap tag giving the date a URL last changed; Google uses it for scheduling recrawls when it is accurate.
lastmod is an optional tag in each sitemap entry that records when the page last meaningfully changed. Its value uses the W3C Datetime format, for example 2026-04-20 or a full timestamp with timezone.
Unlike changefreq and priority, Google does use lastmod — but only when it trusts the value. If the date reflects a real content change, it helps crawlers prioritize pages that have actually been updated. If every URL shows today's date on every crawl, Google learns to ignore the field entirely.
The common mistake is stamping the current time on all URLs whenever the sitemap is regenerated. That destroys the signal. Set lastmod from the page's real modification date, and leave it unchanged when the content has not changed.
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