osoft Bing will rely more heavily on the lastmod date in XML Sitemap files for crawling

Microsoft Bing will begin to rely more on the date that you have specified in your XML sitemap’s lastmod field for crawling. Fabrice Canel, principal product manager at Microsoft Bing stated that Bing will overhaul its crawl scheduling stack starting in June 2023 to make the most of the information provided in the “lastmod” tag in sitemaps.

What is lastmod? The lastmod is the date that the page was last modified as per your XML sitemap file. This is not the date that the URL was created, but rather the date that the page was last modified.

Bing states that lastmod date is crucial. Microsoft Bing stated that the lastmod date is crucial. Fabrice Canel stated that this will improve our crawl efficiency by prioritizing newly updated content and reducing the unnecessary crawling of unmodified content.

The lastmod crawl changes must be live by June 2023.

Bing’s use of lastmod. Bing explained that the “lastmod” tag was used by Bing to indicate when the sitemaps linked to the pages were last modified. This information is used to determine the frequency with which search engines crawl your site and to decide which pages they should index. Search engines can easily identify when a page was updated by including the “lastmod” tag in your sitemap. Search engines will delay crawling new content and may over-crawl your sitemap if they don’t have it.

Lastmod usage statistics. Microsoft Bing also did a study that showed how the lastmod field was used in XML sitemap files across the internet. These are the highlights from that date. Please note that this is based upon Bing’s crawling data.

• 58% of hosts already have an XML sitemap.
  • 
    These sitemaps contain 84% of the lastmod attributes.
    
    • 
      79% have the correct lastmod values.
      
    • 
      18% lastmod values were not set correctly.
      
    • 
      3% only has lastmod values to some URLs.
      
  • These sitemaps have 16% without a lastmod attribute.
• 42% of hosts do not have an XML sitemap

Their biggest problem is the identical lastmod dates in XML sitemaps to all URLs in the file. Bing notices that the date in the lastmod field is being set instead to the date the sitemap was created. This is possible, but it’s highly unlikely for all URLs listed in the XML websitemap file.

Changefreq field. Bing, unlike Google, mostly ignores the changefreq fields in XML sitemaps. In the past, Google claimed it ignored the lastmod date in XML Sitemap files. However, they later stated that they did read it, but might not trust the fully . According to current documentation, Google “uses the value only if it is consistent and verifiable (for instance by comparing to the previous modification of the page).

IndexNow. This advice does not replace Microsoft’s IndexNow initiative. Fabrice Canel wrote, however, that IndexNow was highly recommended for search engines to immediately be informed about any changes to your websites.

Why we care. If you don’t take the lastmod date in your XML websitemap file seriously, then you should. You should be able increase the crawl efficiency of search engines like Bing. This will improve crawl speed, indexing and ranking, as well as your server resources.

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