JavaScript  -  Examples of Web Browser User Agent Strings

CURRENT USER AGENT STRING

The current userAgent string is

 

WINDOWS NT 6.1  -  Windows 7 / Windows Server 2008 R2

AVANT 2012 BUILD 8 (IE Compatible)

....

AVANT 2012 BUILD 8 (IE9 Standards)

....

AVANT ULTIMATE 2012 BUILD 8 (IE Compatible)

....

AVANT ULTIMATE 2012 BUILD 8 (IE9 Standards)

....

AVANT ULTIMATE 2012 BUILD 8 (Mozilla Firefox)

....

CHROME 15.0.874.121

....

CHROME 16.0.912.63

....

FIREFOX 6.0.2

....

FIREFOX 8.0.1

....

INTERNET EXPLORER 9.0.8112.16421 (32-bit)

....

INTERNET EXPLORER 9.0.8112.16421 (64-bit)

....

K-MELEON 1.5.4

....

KONQUEROR 4.7.00 (4.7.0)

....

LUNASCAPE6 ORION (Gecko)

(Lunascape Core Version 6.5.8.24780 / Unicode; Operating System Version 6.1.7601)

Gecko Plugin Version 3.6.24.24768 / Gecko 1.9.2.24

....

LUNASCAPE6 ORION (Trident)

(Lunascape Core Version 6.5.8.24780 / Unicode; Operating System Version 6.1.7601)

Internet Explorer Version 9.0.8112.16421

....

LUNASCAPE6 ORION (WebKit)

(Lunascape Core Version 6.5.8.24780 / Unicode; Operating System Version 6.1.7601)

WebKit Plugin Version 1.3.7.24778 / WebKit 535.1 r91436

....

MAXTHON BROWSER 3.2.2.1000

(Version: 3.2.2.1000 / OS: 6.1.7601.Service Pack 1 / IE: 9.0.8112.16421)

....

OPERA 11.60 (Build 1185)

....

SAFARI 5.1.1 (7534.51.22)

....

SAFARI 5.1.2 (7534.52.7)

....

SEAMONKEY 2.5 (target: i686-pc-mingw32)

 

WINDOWS NT 5.1  -  Windows Fundamentals for Legacy PCs / Windows XP

AVANT 2012 BUILD 8 (IE Compatible)

....

AVANT 2012 BUILD 8 (IE8 Standards)

....

AVANT ULTIMATE 2012 BUILD 8 (IE Compatible)

....

AVANT ULTIMATE 2012 BUILD 8 (IE8 Standards)

....

AVANT ULTIMATE 2012 BUILD 8 (Mozilla Firefox)

....

CHROME 15.0.874.121

 

In computing, a user agent is software, a software agent, that is acting on behalf of a user. For example, an email reader is a Mail User Agent, and in the Session Initiation Protocol (SIP), the term user agent refers to both end points of a communications session. In many cases, a user agent acts as a client in a network protocol used in communications within a client–server distributed computing system. In particular, the Hypertext Transfer Protocol identifies the client software originating the request, using a User Agent header, even when the client is not operated by a user. The SIP protocol, based on HTT, followed this usage. HTTP is used in a wide variety of applications, not only the traditional web-related web browsers, search engine crawlers, also know as spiders, screen readers, and braille browsers used by people with disabilities, applications on mobile phones, but also print drivers and home appliance control. When a software agent operates in a network protocol, it often identifies itself, its application type, operating system, software vendor, or software revision, by submitting a characteristic identification string to its operating peer. In HTTP, SIP, and SMTP/NNTP protocols, this identification is transmitted in a header field User-Agent. Bots, such as web crawlers, often also include a URL and/or e-mail address so that the webmaster can contact the operator of the bot. In HTTP, the User Agent string is often used for content negotiation, where the origin server selects suitable content or operating parameters for the response. For example, the User Agent string might be used by a web server to choose variants based on the known capabilities of a particular version of client software. The User Agent string is one of the criteria by which web crawlers may be excluded from accessing certain parts of a website using the Robots Exclusion Standard, via the robots.txt file. As with many other HTTP request headers, the information in the User Agent string contributes to the information which the client sends to the server, and the string can vary considerably from user to user. The format of the User Agent string in HTTP is a list of product and optional comments. The most important product component is listed first. Unfortunately, during the browser wars, many web servers were configured to only send web pages which required advanced features to clients which were identified as a version of Mozilla. For this reason, most web browsers use a User Agent value as follows: Mozilla/[version] ([system and browser information]) [platform] ([platform details]) [extensions]. The popularity of various web browser products has varied throughout the web's history, and this has influenced the design of websites in such a way websites are sometimes designed to work well only with particular browsers, rather than according to uniform standards by the World Wide Web Consortium (W3C) or the Internet Engineering Task Force (IETF). Websites often include code to detect browser version to adjust the page design sent according to the user agent string received. This may mean that less-popular browsers are not sent complex content, even though they might be able to deal with it correctly, or in extreme cases, refused all content. Thus, various browsers have a feature to cloak or spoof their identification to force certain server-side content. For example, the Android browser identifies itself as Safari in order to aid compatibility. Other HTTP client programs, like download managers and offline browsers, often have the ability to change the user agent string. Spam bots and web scrapers often use fake user agents. At times it has been popular amongst web developers to initiate Viewable With Any Browser campaigns, encouraging developers to design webpages which work equally well with any browser.

A result of user agent spoofing may be collected statistics of web browser usage are inaccurate. The term user agent sniffing refers to the practice of websites showing different content when viewed with a certain user agent. On the internet, this will result in a different site being shown when browsing the page with a specific browser. A useful example of this is Microsoft Exchange Server 2003's Outlook Web Access feature. When viewed with Internet Explorer 6 or newer, more functionality is displayed compared to the same page in older browsers, because older browsers could not render the same content. User agent sniffing is mostly considered poor practice, since it encourages browser-specific design and penalizes new browsers with unrecognized user agent identifications. Instead, the W3C recommends creating HTML markup which is standards compliant, allowing correct rendering in as many browsers as possible, and to test for specific browser features rather than particular browser versions or brands. Web browsers created in the United States, such as Netscape Navigator and Internet Explorer, use the letters U, I, and N to specify the encryption strength in the user agent string. Until the United States government allowed encryption with keys longer than 40 bits to be exported, in 1996, vendors shipped various browser versions with different encryption strengths. "U" stands for "USA," for the version with 128-bit encryption; "I" stands for "International," the browser has 40-bit encryption and can be used anywhere in the world; and "N" stands for "None," no encryption. Following the lifting of export restrictions, most vendors supported 256-bit encryption.