How to recognize it

User agents, as they reach our logs:

Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm) Chrome/116.0.1938.76 Safari/537.36
Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm) Chrome/136.0.0.0 Safari/537.36 AppleWebKit/537.36 (KHTML, like Gecko; compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm) Chrome/116.0.1938.76 Safari/537.36
  • First string: 98% of verified requests. Microsoft says the version number tracks the latest Edge, but Chrome 116 is a 2023 version.
  • Second string: two complete user agents glued together. It is real Bing traffic, verified by reverse DNS.
  • Short form in Microsoft’s docs: absent from our logs in these 8 days:
Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)

Match on bingbot. Microsoft’s BingPreview snapshots use the same bingbot string, so they count as Bingbot too.

  • robots.txt token: bingbot
  • IP list (JSON): bingbot.json
  • Reverse DNS: names ending in search.msn.com, such as msnbot-157-55-33-18.search.msn.com.

What it does

Bingbot is Microsoft’s standard crawler and handles most of Bing’s crawling. Microsoft’s webmaster guidelines tie Copilot to the same content: the NOARCHIVE meta tag keeps a page out of Copilot responses and grounding, and NOCACHE limits Copilot to the page’s URL, title and snippet.

What you gain by allowing it

  • Bing search traffic, and citations with links in Copilot answers built on Bing’s index.

What you lose

By allowing it

  • Crawl load, the third highest among verified crawlers on our sites after ClaudeBot and Googlebot. It can be slowed with Crawl-delay or with Crawl Control in Bing Webmaster Tools, which Microsoft now prefers.
  • Copilot use of your pages, unless you mark them NOARCHIVE or NOCACHE.

By blocking it

  • Bing search and Copilot citations. To stay in Bing but out of Copilot answers, use NOARCHIVE instead of a robots.txt block.

How to verify it

Forward-confirmed reverse DNS:

host 157.55.39.1
host msnbot-157-55-33-18.search.msn.com

The name must end in search.msn.com and resolve back to the same IP. Microsoft also offers a Verify Bingbot tool and the IP list, and says to refresh the list daily. Cloudflare flags the real crawler as a verified bot in the category “Search Engine Crawler”; in our data the flag matched reverse DNS on every request.

Gotchas and history

  • Stale IP list: Microsoft says to refresh bingbot.json daily, but the file’s creationTime on 26 October 2026 was 3 January 2024. Reverse DNS is the safer check.
  • robots.txt groups: a group for bingbot makes Bing ignore everything else in robots.txt. Copy any * rules you still want into it.
  • Two subsystems: Bingbot splits its traffic between two, and only one runs JavaScript; see Bingbot splits traffic between two subsystems.
  • Ads crawler: AdIdxBot, the Bing Ads crawler, uses adidxbot/2.0 in its own user agent; we class it with Bingbot.

What we observed

Data: Cloudflare Logpush for two of our sites, 19-26 October 2026 (8 days).

  • 3,045 requests carried a Bingbot user agent:
    • 2,291 (75%) passed forward-confirmed reverse DNS, all from Microsoft’s network (AS8075);
    • 749 of the 754 fakes came from the Google Cloud scanner;
    • Cloudflare’s verified-bot flag matched our check on all 3,045.
  • 2,250 of the verified requests used Chrome 116 and 36 the glued double string.
  • 1,798 went to the static content site and 493 to the WordPress site. 73 were for /robots.txt.

About Microsoft

  • Bingbot does most of Bing’s crawling, for search and the services built on its index, Copilot included.
  • AdIdxBot crawls ads and the sites they link to, for Bing Ads quality control.
  • BingPreview generates page snapshots for Bing. It sends the bingbot user agent, so logs cannot tell it apart from Bingbot.
  • MicrosoftPreview generates snapshots for Microsoft products, with its own user agent.
  • BingVideoPreview builds video previews in Bing.

Microsoft verifies all of them the same way: reverse DNS to a name ending in search.msn.com, confirmed forward. The control for Copilot is a page tag, not a crawler token. NOARCHIVE keeps a page out of Copilot answers and grounding, and NOCACHE limits Copilot to the URL, title and snippet.

Sources