As AI powered search engines like Bing Copilot continue to reshape how content is discovered and surfaced, keeping your website crawlable, fresh, and fully indexed is more important than ever. While real-time URL submission protocols such as IndexNow help notify search engines of immediate content changes, sitemaps remain a foundational signal for ensuring comprehensive URL coverage across your site.
Scalable Sitemap Support for Large Sites
Bing continues full support of the Sitemap protocol, which allows:
- Up to 50,000 URLs per individual sitemap file.
- Up to 50,000 child sitemap files referenced within a single sitemap index file.
- A single sitemap index file can reference up to 2.5 billion URLs. At scale, multiple index files can support up to 2.5 trillion URLs across a domain, making this approach ideal for large, complex sites.
If you manage a large-scale website, ecommerce platform, or content-rich publishing site, taking full advantage of these limits allows you to ensure all your relevant URLs are discoverable — even at enterprise scale.
Why lastmod Still Matters for AI Powered Indexing
For AI powered search engines like Bing, freshness signals directly influence how quickly updates are reflected in search results and AI generated answers. The lastmod field in your sitemap remains a key signal, helping Bing prioritize URLs for recrawling and reindexing, or skip them entirely if the content hasn’t changed since the last crawl.
To ensure your signals are interpreted correctly, use standard ISO 8601 date formatting for lastmod values, including both the date and time. For example:
Including a timestamp provides a more precise signal of when content was updated, helping Bing prioritize crawling activity more efficiently — especially for frequently updated or time-sensitive pages.
Accurate lastmod values help Bing focus crawling on updated content, a particularly important factor as AI search engines adjust ranking and surfacing in near real time based on content changes. Optional sitemap tags like changefreq and priority are ignored by Bing and do not influence how your content is crawled or ranked.
Tip: Avoid setting lastmod to the time your sitemap was generated unless the content on that URL was actually updated. The value should reflect the true last modification time of the page content, not the sitemap file itself. For additional guidance, see our article on the importance of setting the lastmod tag in your sitemap.
Preferred Sitemap Format for Bing Crawling and Indexing
XML remains the preferred format for sitemaps, as it supports structured metadata like lastmod, which helps Bing assess content freshness and relevance more effectively.
You can also compress your sitemap files using gz format (e.g., sitemaps.xml.gz) to reduce network bandwidth usage and improve submission efficiency.
How to Submit Sitemaps to Bing for Full Coverage
Bing recommends submitting XML sitemaps following the Sitemap specification to help ensure full site discovery and indexing coverage. You can submit your sitemaps through one of these two methods:
- Robots.txt : Include the sitemap location in your site’s robots.txt file for automatic discovery.
Example:
Sitemap: https://www.example.com/sitemap.xml
- Bing Webmaster Tools: Submit your sitemaps directly in Bing Webmaster Tools and monitor indexing performance from your verified account.
When Does Bing Read Your Sitemaps?
Once your sitemap is referenced in your robots.txt file or submitted through Bing Webmaster Tools, Bing will attempt to fetch it immediately upon submission. After that, it will revisit your sitemap on a regular basis, typically at least once per day, to check for updates.
How to Verify That Bing Is Processing Your Sitemaps
To confirm that Bing is reading and using your sitemap:
- Sign in to Bing Webmaster Tools.
- Go to the Sitemaps section for your verified site.
- Review the:
- Submission status (success or error).
- Last read date to confirm it's being accessed regularly.
- Any processing errors that may block indexing.
These checks help ensure your sitemap is accessible and actively supporting Bing’s crawling and indexing—both for traditional search and AI-powered experiences like Copilot.
For full protocol details, visit sitemaps.org.
Strengthen Your Indexing Signals for AI-Powered Search
In today’s AI-powered search landscape, visibility depends on sending the right signals, both in structure and speed. While no tool can guarantee when or how your content will appear in AI-generated results, combining sitemaps and real-time URL submission methods like IndexNow gives your content the best chance to be discovered, crawled, and indexed efficiently.
- Submit a complete XML sitemap through Bing Webmaster Tools, including accurate lastmod values to reflect recent content updates. This helps Bing understand your site’s structure and prioritize crawl activity across your full URL inventory.
- Use IndexNow for real-time URL submission, instantly notifying Bing and participating search engines when individual URLs are added, updated, or removed. This helps ensure changes are surfaced quickly, especially important for freshness in AI search.
- Reference your sitemap in your site’s robots.txt file to support automatic discovery and consistent crawling.
By combining sitemaps for comprehensive site coverage with IndexNow for fast, URL-level submission, you provide the strongest foundation for keeping your content fresh, discoverable, and visible in both traditional and AI-powered search experiences.
Continue to follow the Bing Webmaster Blog for ongoing guidance on indexing, site performance, and evolving strategies for visibility in AI-first search.
Fabrice Canel
Principal Product Manager, Microsoft AI, Bing
Krishna Madhavan
Principal Product Manager, Microsoft AI, Bing
