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".
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So, to get info about your browser, websites often examine the ‘ user agent ’, or ‘UA’ string. An user agent (UA) string is able to be used to detect what version of a specific browser is being used on a certain operating system.
Mapping UA string tokens to a more human-readable browser name for use in code is a common pattern on the web today. When mapping the new Edge token to a browser name, Microsoft recommends using a different name than the one developer used for the legacy version of Microsoft Edge to avoid accidentally applying any legacy workarounds that are not applicable to Chromium-based browsers.
When Microsoft is notified about these types of issues, website owners are contacted and informed about the updated UA. In these cases, Microsoft uses a list of UA overrides in our Beta and Stable channels to maximize compatibility for users who access these sites.
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 useragentstring and consider also the potential risks of using this method to deliver content.
It's easiest to understand user agents if we backtrack and look at the evolution of the web. 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.
That's because Internet Explorer originally had to declare itself to be Mozilla compatible in order to receive content with frames. In practice, the majority of browsers now declare themselves to be Mozilla compatible to ensure that they can access all the content on the web.
More, we can feed that data back into a cycle of continuous improvement, analytics and other processes, like conversion optimization. As we mentioned in the introduction, search engine crawlers are a very specific type of user agent.
An user agent is a particular string of characters in each browser that allows acts as an identification agent. The useragentstring 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).
The useragentstring is a text string that contain the web browser information such as the browser name, version number, if it's a mobile phone, the operating system etc. The useragentstring is used by the websites to provide you the best possible version of the page you're visiting, and for usage statistics (to know the most used browsers, OS...).
User agent refers to the application that remotely accesses a different computer, usually a server, through the network. It means that the Web browser you're using is accessing a program (such as Gmail) or a service (such as Amazon.com) that operates on some other faraway computer.
Your computer (the client) is connecting to the desired Web page (the server) through one of the TCP/IP protocols. When you key in a “query” on your Web browser (user agent) and hit “enter,” a text string (a programming sequence of symbols) is sent to the server of that website.
While the text string identifies itself to the server as an user agent, it simultaneously requests access to the website. When the Internet was young, the World Wide Web was dominated by a few of the first generation of browsers.
As a result, many Web servers were designed to interact and connect with only those leading browsers. This was possible because the website could identify that Web browser as the user agent by its text string when it requested access to the site.
To overcome this roadblock, competing browsers were modified to replicate or impersonate text strings that would be accepted by the website. An early example of this is when the browser Internet Explorer spoofed its primary rival at the time, Netscape Navigator.
Newsreaders, screen readers and other web-related applications and systems act as agents as well. Some websites check the browser version in the user agent to ensure the user has a current browser and directs them to various vendors’ websites to download a newer version.
Many enterprise applications check browser type and versions due mostly to heavy customization of the UI and to ensure an optimal experience. The user is typically denied access without the application’s “certified” browser or is notified the experience will be less than optimal.
The UA string contains details about the browser type, rendering engine, and operating system. For decades, websites have used UA strings to fine-tune features based on a visitor's technical specifications.
For starters, UA strings have been used by online advertisers as a way to track and fingerprint website visitors. To address these issues, Google said it plans to phase out the importance of UA strings in Chrome by freezing the standard as a whole.
The long-term plan is to unify all Chrome UA strings into generic values that don't reveal too much information about a user. The deprecation of the UA string mechanism is part of a push at Google to improve privacy on the web, but without killing online advertising, the lifeblood of most free websites today.