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.
A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".
Using this data, a website can assess the capabilities of your computer, optimizing a page's performance and display. Mozilla/4.0 is used for historical reasons as stated by Microsoft, not to be confused with the variants of Mozilla browsers, such as Firefox.
Noted user agent string with Internet Explorer can have multiple .NET versions. In the past, different encryption versions had to be released for specific parts of the world because of laws in the United States.
However, if you want to gather the information or manipulate the data, it would be better to use a server-side scripting language, such as Perl. Noun (computing) A client application used by an end user, typically for a network protocol such as HTTP or FTP.
By extension, a “reasonable” user agent provides support for core W3C standards, whereas a “somewhat reasonable” user agent supports HTML 32. Moreover, Web browsers not providing support for HTML 3.2 are considered to be, at best, “broken” software.
The term user agent is also used to describe a mail program such as Outlook or Eudora that sends and receives e-mail on a user ’s behalf. Webster's New World Hacker Dictionary Copyright © 2010 by Bernadette Shell and Clemens Martin. Published by Wiley Publishing, Inc., Indianapolis, Indiana.
It may refer to an e-mail client (see messaging system), a Web browser, search engine spider or any other program in the user's machine that is accessing a service on the Internet (see user agent string). Computer Desktop Encyclopedia THIS DEFINITION IS FOR PERSONAL USE ONLY All other reproduction is strictly prohibited without permission from the publisher.
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).
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.
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 ".
The user with this email address already exists. Such phone number is already registered. You can Log in or Restore a password.
Please email us at firstname.lastname@example.org if you think this is en error. They reveal a catalog of technical data about the device and software that the visitor is using.
Armed with this information, you can develop richer and more dynamic websites that deliver different experiences based on the user agent that's visiting. User agents are also critical in controlling search engine robots using the robots.txt file on your server.
In order to leverage this information, you need to understand the component parts of an user agent string and consider also the potential risks of using this method to deliver content. When the internet was a text-based system, right back at the beginning of its use, users had to type commands to navigate and send messages.
We simply point and click, and the browser is acting as our agent,” turning our actions into commands. When your browser (or similar device) loads a website, it identifies itself as an agent when it retrieves the content you've requested.
Browsers : Including Microsoft Edge, Internet Explorer, Firefox, Safari, Chrome, BlackBerry, Opera, Opera Mini, iOS Safari, Chrome for Android, Samsung Internet, HQ browser, and others. Plus a whole range of feed readers, validators, cloud platforms, media players, email libraries, and scripts.
Once the user agent has identified itself to the web server, a process called content negotiation can begin. The user agent application is Mozilla version 5.0, or a piece of software compatible with it.
Note that a huge part of the user agent string is concerned with compatibility. That's because Internet Explorer originally had to declare itself to be Mozilla compatible in order to receive content with frames.
Overall, we can empower our scripts to make the best choice for our visitors, based on their user agent. More, we can feed that data back into a cycle of continuous improvement, analytics and other processes, like conversion optimization.
Chrome Review (Lollipop and above) Mozilla/5.0 (Linux; Android 5.1.1; Nexus 5 Build/LMY48B; WV) Apple WebKit/537.36 (HTML, like Gecko) Version/4.0 Chrome/43.0.2357.65 Mobile Safari/537.36 An user agent is a particular string of characters in each browser that allows acts as an identification agent.
The user agent string contains the user application or software, the operating system (and their versions), the web client, the web client's version, and the engine responsible for the content display (such as Apple WebKit). It is a rendering engine that processes HTML and CSS to interpret and present web pages.