Bing: lastmod Tag & IndexNow for AI Search Indexing
Microsoft Bing says accurate lastmod tags in sitemaps are critical for AI search indexing. Learn why it matters, how IndexNow accelerates updates, and how ShowUpInAI automates it.
TL;DR – Bing just made the
lastmodtag in your XML sitemap non-negotiable for AI search indexing. Combine it with IndexNow for real-time crawling, and let ShowUpInAI handle the automation so you never miss an AI traffic opportunity.
Why Bing’s New Emphasis on lastmod Matters for AI SEO / GEO (Generative AI Optimization)
When Bing’s Webmaster Team reiterated in July 2025 that 84 % of sitemaps already include a lastmod value—but nearly 1 in 5 are wrong—they weren’t just nit-picking. Bing is re-engineering its crawl scheduling stack to rely heavily on lastmod for deciding what to fetch next, especially for its AI-powered experiences like Copilot and ChatGPT’s browsing mode.
AI Crawl Priority
Accurate lastmod dates help Bing prioritize fresh content for AI answers, reducing unnecessary crawling and accelerating discovery in generative AI results.
According to Fabrice Canel (Principal PM at Bing), the rollout will be complete by June 2025, making lastmod a critical ranking and crawling signal for every site that wants to show up in AI answers.
Quick Recap: What Exactly Is lastmod?
<lastmod> is an optional tag inside each <url> block of your XML sitemap that tells search engines the last time a page’s primary content changed. Unlike the deprecated changefreq and priority tags, lastmod is something both Google and Bing actively use—but Bing says it’s about to matter even more for AI indexing.
<url>
<loc>https://www.example.com/best-guide</loc>
<lastmod>2025-07-26T14:32:00+00:00</lastmod>
</url>
Set it only when substantive content changes (not when you tweak a footer date). Bing’s data shows that sitemaps with trustworthy lastmod dates are crawled faster and more efficiently—a win-win for both search engines and site owners.
The Perfect Pairing: lastmod + IndexNow
While lastmod works on a pull model (Bing checks your sitemap on its own schedule), IndexNow flips the script with a push model that instantly alerts participating search engines whenever a URL is added, updated, or deleted.
Key Insight: Bing recommends using IndexNow for immediate updates and relying on daily sitemap checks with correct lastmod dates as a catch-up safety net. Together they form a bullet-proof AI SEO / GEO strategy.
Why You Need Both
- Real-Time Discoverability – IndexNow notifies Bing (and other partners) within minutes, ensuring new content can appear in Copilot and ChatGPT responses almost instantly.
- Efficiency & Sustainability – Accurate
lastmoddates prevent wasteful crawling of unchanged pages, aligning with Bing’s greener web initiative. - Redundancy = Reliability – If an IndexNow ping fails (API limit, server hiccup, wrong key), the sitemap’s
lastmodacts as a reliable fallback.
Implementation Hurdles (and How ShowUpInAI Solves Them)
Setting lastmod correctly for thousands of URLs and generating IndexNow calls every time something changes can get complicated—fast.
Automation Pain Point
Most CMS plugins only update lastmod when the sitemap file regenerates, not when the page content updates—exactly the error Bing warns against.
ShowUpInAI eliminates these headaches by:
- Auto-detecting meaningful content updates and updating
lastmodvalues instantly. - Pushing IndexNow pings across unlimited domains (great for agencies & affiliates).
- Monitoring success rates and retrying failed submissions automatically.
If you’re juggling multiple WordPress, Shopify, or custom sites, let ShowUpInAI handle the grunt work so you can focus on content—not XML syntax.
How to Audit Your lastmod Setup
Fetch Your Current Sitemap
Open /sitemap.xml and look for <lastmod> values. Are they identical? Do they change when you update content?
Validate Dates
Pick a few URLs and verify the date matches the last significant content change—not today’s date.
Implement IndexNow
Generate an API key, host the key file, and send pings whenever content changes. Or use ShowUpInAI automate these steps entirely.
Set Up Monitoring
Track crawl stats in Bing Webmaster Tools to see if updated pages are indexed faster.
Common Mistakes to Avoid
| Mistake | Why It Hurts AI SEO / GEO | How to Fix |
|---|---|---|
| Using today’s date for every URL | Bing will ignore your lastmod values after detecting the pattern | Update only on real content changes |
| Forgetting IndexNow retries | Missed pings delay AI discovery | Use a tool (like ShowUpInAI) with automatic retry logic |
| Single-domain focus | Agencies with dozens of domains can’t scale manual updates | Centralize IndexNow & sitemap automation across all sites |
What Industry Experts Are Saying
"The more websites implement
lastmodin their sitemaps, the search engines—whether AI-driven or rules-based—will increasingly capitalize on this signal. Complimentary, adopt IndexNow to take control of your crawl and SEO game."
— Fabrice Canel, Principal PM, Microsoft Bing (LinkedIn)
The takeaway is clear: lastmod + IndexNow = AI traffic gains. Ignoring either one means slower discovery in Bing’s AI experiences—and soon, potentially in other engines embracing similar models.
Ready to Automate It All?
ShowUpInAI updates your sitemap’s lastmod tags in real-time, sends IndexNow pings the moment content changes, and scales effortlessly across unlimited domains.
Final Thoughts
Bing’s renewed focus on lastmod isn’t just another technical tweak; it’s a strategic shift toward faster, greener, AI-ready discovery. By pairing trustworthy lastmod dates with real-time IndexNow pings—and automating both with ShowUpInAI—you’ll position your site (or your clients’ sites) for maximum visibility in the next wave of AI search.
Try ShowUpInAI free and see how fast you can start getting real ChatGPT user traffic to your site through automated lastmod & IndexNow optimization.
Start Your Free TrialReferences
- Bing Webmaster Blog – “Keeping Content Discoverable with Sitemaps in AI Powered Search” (July 2025)
- Bing Webmaster Blog – “The Importance of Setting the
lastmodTag in Your Sitemap” (Feb 2023) - Search Engine Journal – “Bing Recommends
lastmodTags For AI Search Indexing” (July 2025) - Search Engine Roundtable – “Microsoft Bing:
lastmodTag in XML Sitemap File Is Critical” (Feb 2023) - IndexNow.org – Official Documentation on the IndexNow Protocol
