User Agent 'MSR-ISRCCrawler' (typically from is used by the Microsoft Research (MSR) Internet Services Research Center (ISRC) to analyze the web for Microsoft's Search and Ads services. Having low impact to web sites on the Internet and maintaining a positive relationship with webmasters is extremely important to us. If you have any questions or concerns, please contact us at Our crawler has strict adherence to the http 1.1 protocol, and fully respects robots.txt files as documented at If robots.txt files are malformed, have ambiguous specifications, or do not exist on a given site we conservatively avoid crawling subsets of the site and ensure our crawling waits at least 1 second between requests to be 'polite'. If a site has a robots.txt file the crawler uses the “crawl-delay” parameter as the wait between requests.  Politeness is followed at the IP level of each website we crawl enabling us to be polite to sites that host multiple hosts / domains on a single IP address.

Past uses of our crawler have helped Live Search understand the rate of change of web pages across the Internet to optimize their crawling policy, understand non-404 error pages returned by web sites for missing pages, and to survey robots.txt files across the Internet. The crawler is sometimes used to download all files required to render the page in a web browser, such as the referenced .css and .js files.


Note: the “ISRC” in “MSR-ISRCCrawler” does not stand for International Standard Recording Code.