🤖 Overview

msmobot is a web crawler operated by Microsoft Corporation as part of the Bing search engine infrastructure, specifically designed to index publicly accessible web pages for inclusion in Bing’s search results. It is officially documented on the Bing Webmaster Tools portal as one of Microsoft’s crawlers alongside Bingbot and adidxbot, and its purpose is to discover and fetch content to keep Bing’s index up-to-date. The bot has been active for many years, originally associated with MSN Search, and continues to serve as a primary indexing agent for Bing.

🌐 Technical Behavior

msmobot sends HTTP/1.1 or HTTP/2 GET requests, typically starting from known seed URLs and following internal hyperlinks. It respects the robots.txt directives and the Crawl-Delay header if specified, and Microsoft documentation confirms that it obeys Disallow rules. The crawler uses IP addresses within Microsoft’s AS8075 autonomous system, spanning both IPv4 and IPv6 ranges, with a pool of several hundred distinct addresses. Crawl frequency is dynamic, based on site popularity and server responsiveness; high-traffic sites may be revisited multiple times per day. The bot does not execute JavaScript or render pages, parsing raw HTML to extract text and links, and sends standard HTTP headers including Accept and Accept-Encoding for gzip/deflate compression. It also respects the X-Robots-Tag header for page-level indexing instructions.

📋 robots.txt Compliance

Microsoft officially states that msmobot fully honors robots.txt directives, including Disallow, Allow, and Crawl-Delay settings. Evidence from Bing Webmaster Help documentation shows that webmasters can control the bot’s access by adding rules targeting the “msmobot” User-Agent. No documented evidence exists of the bot ignoring explicit disallow instructions, and it is considered well-behaved in this regard.

🔍 Detection Indicators

The primary identification is the User-Agent string, typically Mozilla/5.0 (compatible; msmobot/1.0; +http://search.msn.com/msmobot.htm). Variations include “msmobot/2.0” or strings lacking the Mozilla prefix. The bot rarely sends a Referer header and may include a From header pointing to a Microsoft contact address. Behavioral fingerprints include a high request rate from a single IP, use of standard HTTP methods (GET/HEAD), and a focus on textual content rather than images or other media.

📊 Data Usage

The collected data is used exclusively for Bing search indexing — text, links, and metadata are processed to build and update the search engine’s index, enabling Bing to return relevant results. Microsoft may also leverage the crawled data to improve search algorithms, detect spam, and enhance the overall search experience. While not directly used for training large language models, Bing’s AI features (such as Copilot) may draw from the indexed content indirectly.

⚙️ Rate Limiting Policy

Although msmobot is a legitimate, non-malicious crawler, it can generate significant traffic, especially on sites with deep link structures. Rate limiting is recommended to prevent excessive resource consumption, but outright blocking is discouraged as it degrades search visibility. Using robots.txt Crawl-Delay is the preferred method, with threshold-based rate limiting (e.g., limiting requests per second from its IP range) as an acceptable alternative.

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the bots listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.