lastmod is an optional field in an XML sitemap that states when the content of a URL last changed. Search engines can use it to decide which pages to recrawl.
How is lastmod used?
The sitemaps protocol expects the date of the last change of the page, in W3C Datetime format. A date alone is valid, and a timestamp with time zone is more precise. Google says it uses the value if it is consistently and verifiably accurate, for example when compared with the page’s actual last modification. It means significant changes to the main content, structured data or links. A new copyright year in the footer does not count.
Bing calls lastmod an especially important signal for crawl frequency and indexing priority. Google ignores the changefreq and priority fields.
| Type | Purpose | Limits | Required elements |
|---|---|---|---|
| XML sitemap | a file with information about the pages, videos and other files on a site and the relationships between them | at most 50,000 URLs or 50 MB (uncompressed) per file; UTF-8, absolute URLs | urlset, and per URL a url with loc |
| Sitemap index | groups several sitemaps so they can be submitted together | at most 50,000 sitemaps and 50 MB per index; up to 500 index files per site in Search Console | sitemapindex, and per sitemap a sitemap with loc |
| Image sitemap | tells Google about images it might not otherwise find, such as images loaded with JavaScript | up to 1,000 image:image per url; otherwise as for XML sitemaps | image:image with image:loc |
| Video sitemap | adds information about videos hosted on the pages | as for XML sitemaps; description at most 2,048 characters | video:video with video:thumbnail_loc, video:title, video:description and either video:content_loc or video:player_loc |
| News sitemap | tells Google about news articles with extra details | up to 1,000 news:news per file; only articles from the last two days | news:news with news:publication (news:name, news:language), news:publication_date, news:title |
| Sitemap with hreflang | lists the language and regional versions of a page | as for XML sitemaps | per url a loc and one xhtml:link rel="alternate" hreflang="…" for every version, including the page itself |
| HTML sitemap | a page of links for visitors to the site | – (not part of the sitemap protocol; Google says it cannot be submitted as a sitemap. Source: Google Search Central Blog, 2005) | – |
Image, video, news and hreflang data are extensions of the XML format; every file is limited to 50,000 URLs or 50 MB. Of the optional elements, Google uses lastmod if it is consistently and verifiably accurate and ignores priority and changefreq. The HTML sitemap details come from a 2005 Google blog post; Google's current sitemap documentation does not mention HTML sitemaps. Sources: Google Search Central: Build and submit a sitemap (last updated 2025-12-10); Google Search Central: Manage your sitemaps with sitemap index files; Google Search Central: Image sitemaps; Google Search Central: Video sitemaps; Google Search Central: Create a news sitemap; Google Search Central: Localized versions of your pages (sitemap method); sitemaps.org: Sitemaps XML format; Google Search Central Blog (2005): How is a Google Sitemap different from an HTML sitemap?. Last checked: .
Example
<url>
<loc>https://example.com/guides/sitemaps/</loc>
<lastmod>2026-10-06T09:15:00+02:00</lastmod>
</url>
Common mistakes
Some CMS setups write the current date for every URL each time the sitemap is generated. The value then no longer matches the last real change, which is the match Google asks for (assessment of common CMS behavior).
Sources
- Build and submit a sitemap – Google Search Centraldevelopers.google.com
- sitemaps.org protocolsitemaps.org
- The Importance of Setting the lastmod Tag in Your Sitemap – Bing Webmaster Blog (Feb 2023)blogs.bing.com
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