Internet Explorer 8 User-Agent String

As Dean announced, a beta version of Internet Explorer 8 will be released in the first half of 2008. The HTTP headers of every web request contain a simple string called the "User-Agent" that allows servers to identify the type and version of the visitor’s browser.  For a deeper understanding of the User-Agent string, please see […]

As Dean announced, a beta version of Internet Explorer 8 will be released in the first half of 2008. 

The HTTP headers of every web request contain a simple string called the "User-Agent" that allows servers to identify the type and version of the visitor’s browser.  For a deeper understanding of the User-Agent string, please see Understanding User-Agent Strings.

When released, the IE8 beta will introduce an updated User-Agent string.  For IE8, we’ve simply replaced "MSIE 7.0" with "MSIE 8.0".  For example, on Windows Vista, IE8 sends:

Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0)

Best Practices: Websites that are sensitive to changes in the User-Agent string may need to be updated to support IE8. 

During internal testing, we have encountered a small number of sites which fail to recognize IE8 because they are performing exact string matches to look for specific IE version strings. Those checks will need to be removed or updated to accommodate IE8.  The article Best Practices for detecting the Internet Explorer version provides suggestions and code samples.

As noted in the Best Practices article, it is not recommended that you block access to content based on the user-agent string of the browser. If you do have to offer different content to different versions of the browser due to improved capabilities, you should ensure that future versions of the browser are not blocked. Serving content based solely on the user-agent string is often an unreliable way to detect the full capabilities of the browser, because the user might have adjusted some settings, such as disabling script or extensions.

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Microsoft, Internet Explorer 8, IE8, User-Agent, Beta, Browser