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".
There's no “standard” way of writing an user agent string, so different web browsers use different formats (some are wildly different), and many web browsers cram loads of information into their user agents. Some mobile web browsers will let you change what the browser identifies itself as (i.e. “Mobile Mode” or “Desktop Mode”) in order to access certain websites that only allow desktop computers.
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.
UAS also tell the sites you’re visiting some browser related software which you may have installed. So if we had a special section for Vista users, we could redirect this person based on the Windows NT 6.0 string to a subsection in our site related strictly to Vista.
Having the knowledge from above, Sergeant Spoofing is used by many programmers that don’t want people to know how they’re getting to the site(s). UA scan be blank, or contain custom information like a URL to a site that might promote a particular browser or script.
You may have reached us looking for answers to questions like: How to find the user agent string. So, to get info about your browser, websites often examine the ‘ user agent ’, or ‘UA’ string.
This page displays your Sergeant String and Screen Resolution. This is a very basic output of the Sergeant also referred to as simply UA.
Sites are able to detect your UA and redirect to a more fitting page for your browser if desired. UAS also tell the sites you're visiting some browser related software which you may have installed.
So if we had a special section for Vista users, we could redirect this person based on the Windows NT 6.0 string to a subsection in our site related strictly to Vista. UA scan be blank, or contain custom information like a URL to a site that might promote a particular browser or script.
User agent is an HTTP request header string identifying browser, application, operating system which connects to the server. Not only browsers have user agent but also bots, search engines crawlers such as Google bot, Google AdSense etc.
Most fields using product tokens also allow sub-products which form a significant part of the application to be listed, separated by white space. The tokens are typically listed by significance, however this is completely left up to software publisher.
In summary, it is not a very standardized format, and as we will see, has evolved into a fairly chaotic environment that can be only unraveled by sustained and dedicated attention to mapping and interpreting this entropy. One of the main use cases of an user agent parser is to identify and handle requests from certain types of traffic.
This is particularly useful when dealing with the wide spectrum of devices in use today, and allows you to get as fine-grained as you like with your content targeting strategy. Outside of web optimization, this has obvious applications to the advertising sector, where the device can be useful as a criterion for targeting.
Bots and crawlers have User -Agents too, and can be identified accurately by a good device detection solution. Security is the other big area where being aware of the nature of traffic hitting your services is extremely important.
These range from search engines to link checkers, SEO tools, feed readers, scripts and other nefarious actors at large in the web landscape. Being able to distinguish between these different sources can provide significant savings in IT costs by detecting and identifying bot traffic to your site.
You would need to constantly update your regex rules as new devices, browsers and OSs are released, and then run tests to see if the solution still works well. At some point, this becomes a costly maintenance job, and, over time, a real risk that you are misdirecting or failing to detect much of your traffic. Accurately parsing User -Agents is one problem.
Device Atlas uses a Patricia train data structure to determine the properties of a device in the quickest and most efficient way. This is the reason why major companies rely on established solutions built on proven and patented technology like Device Atlas.