What Does Your User Agent Say About You?


A user agent is a computer program representing a person, for example, a browser in a Web context.

Besides a browser, a user agent could be a bot scraping webpages, a download manager, or another app accessing the Web. Along with each request they make to the server, browsers include a self-identifying User-Agent HTTP header called a user agent (UA) string. This string often identifies the browser, its version number, and its host operating system.

Spam bots, download managers, and some browsers often send a fake UA string to announce themselves as a different client. This is known as user agent spoofing.

The user agent string can be accessed with JavaScript on the client side using the navigator.userAgent property.

A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".


User Agent String

Browser Data

History Of User Agent

James Smith
• Tuesday, 05 July, 2022
• 13 min read

And behold, then came a new web browser known as “Mozilla”, being short for “Mosaic Killer,” but Mosaic was not amused, so the public name was changed to Netscape, and Netscape called itself Mozilla/1.0 (Win3.1), and there was more rejoicing. And so Microsoft made their own web browser, which they called Internet Explorer, hoping for it to be a “Netscape Killer”.

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And Microsoft grew impatient, and did not wish to wait for webmasters to learn of IE and begin to send it frames, and so Internet Explorer declared that it was “Mozilla compatible” and began to impersonate Netscape, and called itself Mozilla/1.22 (compatible; MSI 2.0; Windows 95), and Internet Explorer received frames, and all of Microsoft was happy, but webmasters were confused. And Microsoft sold IE with Windows, and made it better than Netscape, and the first browser war raged upon the face of the land.

And Gecko began to multiply, and other browsers were born that used its code, and they called themselves Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; RV:1.7.2) Gecko/20040825 Camino/0.8.1 the one, and Mozilla/5.0 (Windows; U; Windows NT 5.1; DE; RV: Gecko/20071008 Monkey/1.0 another, each pretending to be Mozilla, and all of them powered by Gecko. And Microsoft feared Firefox greatly, and Internet Explorer returned, and called itself Mozilla/4.0 (compatible; MSI 8.0; Windows NT 6.0) and it rendered good code, but only if webmasters commanded it to do so.

Its syntax was defined as the software product name, with an optional slash and version designated “. The prose already invited people to use it for analytics and identify the products with implementation issues.

Updating databases and algorithms for identifying correctly is a very high maintenance task which is doomed to fail at a point in the future. New solutions are being developed for helping people to adjust the user experience depending on the capabilities of the products, not its name.

Responsive design helps to create Websites that are adjusting for different screen sizes. You could fall in the same traps as the ones existing with user agent detection algorithms.

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User agent detection leads to situation where a new player can hardly enter the market even if it has the right set of technologies. Remember that there are huge benefits to create a system which is resilient to many situations.

We recommend you to limit your detection to the simplest possible string by matching the substring mob in lowercase. Remember that whatever the number of tokens you put there, you will fail at a point in the future.

There will be many road blocks on the way depending on the context, the business requirements, the social infrastructure of your own company. He regularly also blogs at and loves to travel and meet people.

During the first browser war, many web servers were configured to send web pages that required advanced features, including frames, to clients that were identified as some version of Mozilla only. Other browsers were considered to be older products such as Mosaic, Cello, or Samba, and would be sent a bare-bones HTML document.

Automated agents are expected to follow rules in a special file called robots.txt “. 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 that 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).

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Websites often include code to detect browser version to adjust the page design sent according to the user agent string received. 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 (among other things) in order to aid compatibility. User agent sniffing is the practice of websites showing different or adjusted content when viewed with certain user agents.

An 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 any other browsers.

Web browsers created in the United States, such as Netscape Navigator and Internet Explorer, previously used the letters U, I, and N to specify the encryption strength in the user agent string. Until 1996, when the United States government disallowed encryption with keys longer than 40 bits to be exported, vendors shipped various browser versions with different encryption strengths.

^ a b RFC 3261, SIP: Session Initiation Protocol, IETF, The Internet Society (2002) ^ RFC 7231, Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content, IETF, The Internet Society (June 2014) ^ Net news Article Format. Browser Versions Carry 10.5 Bits of Identifying Information on Average “, Electronic Frontier Foundation, 27 January 2010.

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I've been rejected until I come back with Netscape” ^ “Android Browser Reports Itself as Apple Safari”. ^ User Agent String explained: Android WebKit Browser”.

Mozilla/5.0 (Linux; U; Android 2.2; ends; HTC_DesireHD_A9191 Build/FRF91) Apple WebKit/533.1 (HTML, like Gecko) Version/4.0 Mobile Safari/533.1 ^ Emberton, Stephen. ^ “Chrome Phasing out Support for User Agent ".

Essentially, an user agent is a way for a browser to say “Hi, I’m Mozilla Firefox on Windows” or “Hi, I’m Safari on an iPhone” to a web server. The user agent string identifies the browser as IE 9 with the Trident 5 rendering engine.

The plot thickens: Chrome is pretending to be both Mozilla and Safari. To understand why, we’ll have to examine the history of user agents and browsers.

(Yes, this means that you can sometimes bypass registration screens by setting your user agent to Google bot.) He's written about technology for nearly a decade and was a World columnist for two years.

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Chris has written for The New York Times, been interviewed as a technology expert on TV stations like Miami's NBC 6, and had his work covered by news outlets like the BBC. Since 2011, Chris has written over 2,000 articles that have been read more than 500 million times---and that's just here at How-To Geek.

Mozilla/5.0 (Mac­in­tosh; Intel Mac OS X 10_12_6) Apple WebKit/604.5.6 (HTML, like Gecko) Version/11.0.3 Safari/604.5.6 Except that for com­pat­i­bil­i­ty, they all lie a bit to try to get the best web pages pos­si­ble.

Generally speaking, as with Gecko, it’s typical to determine that a browser is WebKit-based rather than trying to identify Safari specifically. Conqueror, the browser bundled with the KBE Linux desktop environment, is based on the HTML open-source rendering engine.

It’s worth nothing that this claim has already shot themselves in the foot, and so Chrome now spoofs Safari for Hotmail. Chrome isn’t the only one that does this sort of thing, there’s a lot that goes on behind the scenes of browsers for compatibility reasons.

Mar 11, 2018 22:00:00 Browser ling A user agent is software that has a function to communicate based on a protocol and notify the result on behalf of a user, and generally refers to a web browser. “Netscape” was compatible with frame functions that NASA Mosaic did not support.


The web page administrator who incorporated the frame function into the web page says, “I want to visit from a Netscape browser with a frame function, but I do not want to visit from other browsers that do not support the frame function.” We have developed a system that identifies the user agent character string” of the browser that visited the website, and that only the user agent browser permitted by the web page administrator can visit the web page. Tonynetone Inspired by Netscape's breakthrough, Microsoft announced a web browser called Internet Explorer with the release of Windows 95.

However, because Microsoft had a strong desire to “spread Internet Explorer as soon as possible to make it a“ Netscape killer ””, users were able to visit the web page through user agent sniffing by the web page administrator. Internet Explorer users welcomed the advent of Windows-compatible browsers, but the web page administrator was very confused.

Microsoft is rapidly expanding its browser share by selling Internet Explorer together with Windows. User agent sniffing was once again carried out, and web pages that favored Gecko-based browsers appeared.

In addition, Opera, a web browser developed in Norway, was able to 'change user agent strings' from the beginning. I’m currently getting ready to go do some volunteering in my son’s 5th grade class, teaching them some basic Web stuff, and thinking back to those early days has me feeling nostalgic.

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