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".
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.
navigator.sergeant : This method reads the navigator object when the page load is finished. navigator.sergeant : This method clones the “navigator” object exactly when page is about to render to prevent any external scripts from altering it later.
Tab : Could be one of “navigator”, “UA_prayer”, “platform_JS” which indicates the default rendering engine that is used to display the results. Verbose : Could be one of “true” or “false” values which indicates whether the page uses all methods or just the active one.
User agents are the strings of text which specify the browser and operating system of web servers. User agents are present in HTTP headers when the browser wants to communicate with a server.
Each browser has its specific user agent string and web servers utilize this information to deliver appropriate material across different operating systems. An example of this is the mobile version of webpages in devices; usually slimmed down and organized vertically for user ease.
Web servers provide the bots with special treatments and verifications such as mandatory registrations, screens, etc. Mozilla was considerably more advanced in terms of connectivity and security than Mosaic because of the ease of supported frames it provided.
This was a remarkable advancement considering the other browsers made use of sending old pages without any frames at all. However, there was still no receiving end of webpages with frames, because they were just shared with Mozilla browsers.
Armed with this information, you can develop richer and more dynamic websites that deliver different experiences based on the user agent that is visiting. When your browser (or similar device) loads a website, it identifies itself as an agent when it retrieves the content you have requested.
This feature is useful for SEO professionals, for example, to identify issues with cloaking which is against Google’s Webmaster Guidelines or auditing websites which has different look depending on the device. User agent is an HTTP request header string identifying browser, application, operating system which connects to the server.
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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.