Lastmod support in WordPress 6.5 refers to the native inclusion of the lastmod element in sitemaps. This element indicates the last significant modification date of a webpage, which helps search engine crawlers prioritize and schedule their crawls more efficiently. By having this field automatically populated, WordPress 6.5 allows websites to improve their SEO efforts without the need for additional manual configuration.

To improve crawl efficiency for search engines using WordPress 6.5, website owners should upgrade to this version to take advantage of the native lastmod support. This feature automatically updates the lastmod element in sitemaps, which signals to search engines when significant changes have been made to a page, allowing them to crawl the site more efficiently and keep up with the most current content.

Google's Gary Illyes recommends upgrading to WordPress 6.5 because it introduces native support for the lastmod element in sitemaps, which is a key signal for search engine crawlers to understand the frequency of page updates. This can lead to more efficient crawling and potentially better SEO performance. Illyes emphasizes the importance of keeping WordPress installations updated to ensure websites are in line with SEO best practices.