> ## Content Index > Fetch the complete content index at: https://www.boldoutlook.com/llms.txt > Use this file to discover other available public pages before exploring further. # Bing Pushes lastmod Tags as Key Signal for AI-Driven Search Indexing - URL: https://www.boldoutlook.com/bing-pushes-lastmod-tags/ - Published: 2025-07-31T20:00:42.000Z - Updated: 2025-07-31T20:00:42.000Z - Description: Bing urges site owners to use accurate lastmod tags in sitemaps as a top signal for AI-powered indexing. Combined with IndexNow, this helps keep content fresh and discoverable—especially for large or frequently updated sites navigating the future of AI-driven search. - Author: Brandon Himpfen - Tags: Bing, Bing Search, Technical SEO, AI, SEO, SEO News, AI Search, Sitemaps, IndexNow, lastmod Tag, Crawl Budget, Microsoft AI, Digital Marketing, Scalable SEO, #Import 2026-10-18 13:20 As search continues its evolution into the [AI](https://www.boldoutlook.com/tag/ai/) era, Microsoft’s [**Bing**](https://www.boldoutlook.com/tag/bing/) is doubling down on a simple but powerful signal: the **`lastmod` tag** in XML sitemaps. In a [recent update](https://blogs.bing.com/webmaster/July-2025/Keeping-Content-Discoverable-with-Sitemaps-in-AI-Powered-Search) to its official sitemap guidance, Bing emphasized that this tag plays a **critical role in AI-powered indexing**, helping its systems decide **what to recrawl and when.** For site owners and SEOs alike, this is a strong reminder that [**technical SEO**](https://www.boldoutlook.com/tag/technical-seo/) **fundamentals still matter—especially in the age of AI.** ## Why `lastmod` Now Matters More Than Ever At its core, the `lastmod` tag tells search engines **when a page was last meaningfully updated**. For years, it’s been a quiet player in the sitemap spec, often underutilized or misused. But Bing now says that **`lastmod` is a “top signal”** for its AI-powered crawling system. The guidance makes it clear: if you want Bing to **prioritize crawling the right pages**, especially on large or frequently updated sites, your sitemaps should contain **precise and accurate `lastmod` values**. > ✅ **Format tip:** Use the ISO 8601 standard with both **date and time**, e.g. `2004-10-01T18:23:17+00:00`. Critically, **don’t just set `lastmod` to the time your sitemap was generated**—that’s a common mistake that can lead to unnecessary crawling or indexing inefficiencies. Bing is urging site owners to **only update `lastmod` when content has actually changed.** ## What Doesn’t Matter Anymore: `changefreq` and `priority` In the same update, Bing confirmed what many [SEO](https://www.boldoutlook.com/tag/seo/)s already suspected: the **`changefreq`** and **`priority`** fields in sitemaps are now **ignored.** These fields were intended to indicate how often a page is likely to change and how important it is compared to other pages. But in practice, they’ve been **inconsistent and unreliable** across sites—so Bing’s AI-driven systems no longer use them. ## How to Submit and Monitor Your Sitemap Bing recommends two standard ways to submit sitemaps: - Reference it in your `robots.txt` file. - Submit directly via [Bing Webmaster Tools](https://www.bing.com/webmasters/about). Once submitted, Bing **fetches the sitemap immediately** and continues to **check it daily** for updates. Within Webmaster Tools, you can view: - Submission status. - Last read date. - Any processing or parsing errors. This allows you to verify if your sitemap is being properly interpreted and contributing to better indexation. ## Pairing Sitemaps with IndexNow for Speed While sitemaps offer broad visibility into your site structure, **IndexNow**—Microsoft’s real-time indexing protocol—lets you **instantly ping Bing** when a specific page is added, updated, or deleted. Bing recommends using **both** to get the best of both worlds: - **Sitemaps** for full site structure. - **IndexNow** for fast, URL-specific updates. > “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,” Bing’s team explained. **Editorial Insight**: For SEOs and developers already juggling crawl budget strategies for [Google](https://www.boldoutlook.com/tag/google/), IndexNow offers a compelling advantage for [**Bing**](https://www.boldoutlook.com/tag/bing/)**, Yandex, and other adopters**—especially when you’re dealing with high-volume content or time-sensitive updates. ## Designed to Scale: Trillions of URLs Supported For enterprise websites, publishers, and ecommerce giants, scale matters. Fortunately, Bing’s sitemap protocol is built to handle **trillions of URLs**, with support for: - 50,000 URLs per sitemap. - 50,000 sitemaps per index file. - 2.5 billion URLs per index. - Multiple index files for up to 2.5 trillion URLs. That level of capacity makes it possible for massive platforms to maintain comprehensive, optimized sitemap structures without compromise. > According to **Fabrice Canel** and **Krishna Madhavan** of Microsoft AI and Bing, using these limits to their full extent helps keep large-scale content **discoverable and competitive in AI-powered search.** ## Why This Matters: SEO in the AI Age Bing’s renewed emphasis on `lastmod` is more than a technical update—it’s a strategic signal about **where search is heading**. In a world where AI systems are constantly evaluating which content is **current, helpful, and worth surfacing**, **accurate metadata** becomes a key input for smart crawling and ranking decisions. For marketers and SEO professionals, the message is clear: - Don’t neglect your sitemaps. - Keep `lastmod` precise and truthful. - Embrace real-time tools like IndexNow. - Avoid outdated tags like `priority` and `changefreq.` Whether you’re running a small [blog](https://www.boldoutlook.com/tag/blogging/) or a global [e-commerce](https://www.boldoutlook.com/tag/e-commerce/) platform, this level of clarity gives your content the best shot at being **indexed quickly and accurately** in the AI search landscape.