Should You Really Update the lastmod Tag in Your XML Sitemap?

The lastmod tag in an XML sitemap is supposed to indicate to Google the date a page was last modified. In theory, this information helps the search engine prioritize crawling of recently updated content.

However, Google specifies that this tag is only useful if it reflects significant changes to the content. A simple layout modification, comment addition, or cosmetic change doesn't justify updating lastmod.

The main problem identified concerns CMS and automated systems that generate identical dates for all pages, or that update lastmod with each server request. These practices render the information totally useless to Google, which ends up completely ignoring these signals when they lack consistency.

• Google uses lastmod only if the data is consistent and verifiable
• Only substantial content modifications deserve an update
• Automatically generated and identical dates are ignored by the search engine
• Improper use of lastmod can harm the credibility of your sitemap

This position from Google is perfectly consistent with field observations. Sites that update lastmod for every minor modification (typographical correction, CSS adjustment) see no advantage in terms of crawling or indexing.

The important nuance concerns the definition of a "significant change". In practice, this includes: adding substantial sections, updating important factual data, completely rewriting an article, or adding enriching media. Simply adding two sentences is generally not enough.

For news sites or e-commerce with frequent and real updates, lastmod remains relevant. For corporate sites with few changes, it's better to only populate this tag during genuine content overhauls.

• Audit your CMS: Check if lastmod is automatically generated and whether dates correspond to actual modifications
• Disable automatic updates: If your system modifies lastmod without valid reason, disable this functionality
• Define a modification threshold: Establish a clear internal rule on what constitutes a significant change (e.g., 20% of content modified)
• Clean up your current sitemap: Remove or correct inconsistent lastmod dates that harm your credibility
• Implement a versioning system: Document major modifications to justify lastmod changes
• Prioritize quality over quantity: Better not to populate lastmod than to provide erroneous information
• Monitor crawl impact: Use Search Console to verify if your modifications influence crawl frequency