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".
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. Changing the user agent string can be useful in certain scenarios when some website's functionality is locked down to the specific platform and you need to bypass the restriction.
This allows developers to differentiate various device classes like tablets, phones, Desktop PCs and laptops, and more. The user agent string can provide web servers some details about the user's operating system, and the browser version.
However, if the user agent reports Linux, Android or iOS, you will see direct download links to ISO files. Choose the desired web browser to change the user agent string.
The list includes various versions of Internet Explorer, along with Opera, Safari, Firefox, and Chrome. Using the built-in Developer Tools option, you can change the user agent in Microsoft Edge any time.
You can change the user agent of Microsoft Edge via Developer Tools menu. As mentioned earlier above, changing user agent in Microsoft Edge is extremely easy.
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.
Get our daily newsletter from SEJ's Founder Loren Baker about the latest news in the industry! The new Microsoft Edge running on Chromium isn’t yet here officially, but a leaked build allows us to try out the browser in anticipation of its highly-anticipated release.
Using the browser on a daily basis isn’t obviously recommended as experimental builds like this can’t by any means become your main driver. For many users, switching to a different user agent and thus emulating another browser is a method to bypass certain website restrictions that concern a specific app.
For example, if a website doesn’t support Chromium, you can very well change the user agent to mimic a different browser like Mozilla Firefox. The best example is Skype for Web, which doesn’t work in Firefox anymore, so Mozilla users need to switch to another user agent to connect to the service.
For those unfamiliar with this screen, it’s specifically supposed to provide developers with advanced tools that let them analyze code and website performance. Changing the user agent is actually considered a developer option that helps webmasters check their pages against potential compatibility issues with different browsers.
By default, Microsoft Edge is configured to Select automatically the user agent, so you need to uncheck this option to be able to choose a custom setting. It's easy to search the millions of user agents we've got with the API.
There is protection in place to stop the scraping of these user agent listings. We've had to do this because otherwise we get constantly overrun by inconsiderate or malfunctioning bots which overload the system.
As such, we're forced to block traffic from popular web hosting companies, VPNs and Proxies, we also rate limit requests and have some other checks too. If you need to get access to the listings of user agents you can either get them in an easy-to-use database download or via the API.
There are ways to develop your website to progressively enhance itself based on the availability of features rather than by targeting specific browsers. Using the user agent to detect the browser looks simple, but doing it well is, in fact, a very hard problem.
Also, experts, or people with another point of view, can give you ideas for working around the bug. If the problem seems uncommon, it's worth checking if this bug has been reported to the browser vendor via their bug tracking system (Mozilla ; WebKit ; Blink ; Opera).
Your site needs to use a specific Web feature that some browsers don't yet support, and you want to send those users to an older Website with fewer features but that you know will work. This is the worst reason to use user agent detection because odds are eventually all the other browsers will catch up.
In those rare cases where behavior differs between browsers, instead of checking the user agent string, you should instead implement a test to detect how the browser implements the API and determine how to use it from that. Support could have been added to other browsers at any time, but this code would have continued choosing the inferior path.
As the above code demonstrates, there is always a way to test browser support without user agent sniffing. For example, in the above code snippets, using look behind in short-regexp notation (e.g. /reg/IGM) will cause a parser error in unsupported browsers.
Progressive enhancement This design technique involves developing your Website in 'layers', using a bottom-up approach, starting with a simpler layer and improving the capabilities of the site in successive layers, each using more features. Graceful degradation This is a top-down approach in which you build the best possible site using all the features you want, then tweak it to make it work on older browsers.
Rather, add in touch conveniences such as bigger, more easily clickable buttons (you can do this using CSS by increasing the font size). Here is an example of code that increases the padding of #exampleButton to 1em on mobile devices.
This effect can be easily achieved using CSS flex boxes, sometimes with floats as a partial fallback. Also try to move less relevant/important information down to the bottom and group the page's content together meaningfully. Although it is off-topic, perhaps the following detailed example might give you insights and ideas that persuade you to forgo user agent sniffing.
The boxes can be separated into multiple columns via two equally fair method. The second method uses a Column layout and resents all the dogs to the left and all the cats to the right.
Only in this particular scenario, it is appropriate to provide no fallback for the flex boxes/multi columns, resulting in a single column of very wide boxes on old browsers. If more people visit the webpage to see the cats, then it might be a good idea to put all the cats higher in the source code than the dogs so that more people can find what they are looking for faster on smaller screens where the content collapses down to one column. Next, always make your code dynamic.
The user can flip their mobile device on its side, changing the width and height of the page. Or, there might be some weird flip-phone-like device thing in the future where flipping it out extends the screen.
The simplest way to do this is to separate all the code that moves content around based on screen size to a single function that is called when the page is loaded and at each resize event thereafter. Also note that there is a huge difference between the media queries (max-width: 25em), not all and (min-width: 25em), and (max-width: 24.99em) : (max-width: 25em) excludes (max-width: 25em), whereas not all and (min-width: 25em) includes (max-width: 25em).
Internet Explorer (on Windows) and WebKit (on iOS) are two perfect examples. WebKit is a bit worse because Apple forces all the browsers on IOS to use WebKit internally, thus the user has no way to get a better more updated browser on older devices.
For example, WebKit 6 has a bug whereby when the device orientation changes, the browser might not fire MediaQueryList listeners when it should. Most browsers set the name and version in the format BrowserName/VersionNumber, with the notable exception of Internet Explorer.
So to detect Safari you have to check for the Safari string and the absence of the Chrome string, Chromium often reports itself as Chrome too or Sea monkey sometimes reports itself as Firefox. Also, pay attention not to use a simple regular expression on the BrowserName, user agents also contain strings outside the Keyword/Value syntax.
Must containment not containFirefoxFirefox/xyzSeamonkey/xyzSeamonkeySeamonkey/xyzChromeChrome/chromium/xyzChromiumChromium/xyzSafariSafari/chrome/XYZ or Chromium/safari gives two version numbers: one technical in the Safari/XYZ token, and one user -friendly in a Version/XYZ tokenizer Opera 15+ (Blink-based engine) The browser version is often, but not always, put in the value part of the BrowserName/VersionNumber token in the Sergeant String.
There are five major rendering engines: Trident, Gecko, Presto, Blink, and WebKit. It is therefore important to pay attention not to trigger false-positives when detecting the rendering engine.
Must containGeckoGecko/xyzWebKitAppleWebKit/pay attention, WebKit browsers add a 'like Gecko' string that may trigger false positive for Gecko if the detection is not careful. PrestoOpera/XYZ Note: Presto is no longer used in Opera browser builds >= version 15 (see 'Blink')Trident Trident/Internet Explorer put this token in the comment part of the Sergeant StringEdgeHTML Edge /the non-Chromium Edge puts its engine version after the Edge / token, not the application version. Note: Edge HTML is no longer used in Edge browser builds >= version 79 (see 'Blink'). BlinkChrome/XYZ Most rendering engines put the version number in the RenderingEngine/VersionNumber token, with the notable exception of Gecko.
The Operating System is given in most Sergeant strings (although not web-focused platforms like Firefox OS), but the format varies a lot. They indicate the OS, but also often its version and information on the relying on hardware (32 or 64 bits, or Intel/PPC for Mac).
Like in all cases, these strings may change in the future, one should use them only in conjunction with the detection of already released browsers. A technological survey must be in place to adapt the script when new browser versions are coming out.
The most common reason to perform user agent sniffing is to determine which type of device the browser runs on. Never assume that a browser or a rendering engine only runs on one type of device.
Never use the OS token to define if a browser is on mobile, tablet or desktop. Internet Explorer Immobile/XYZ token in the comment. Mozilla/5.0 (compatible; MSI 9.0; Windows Phone OS 7.5; Trident/5.0; Immobile/9.0) Edge on Windows 10 Mobile/XYZ & Edge / tokens outside the comment. Mozilla/5.0 (Windows Phone 10.0; Android 6.0.1; Xbox; Xbox One) Apple WebKit/537.36 (HTML, like Gecko) Chrome/58.0.3029.110 Mobile Safari/537.36 Edge /16.16299In summary, we recommend looking for the string “Mob” anywhere in the Sergeant to detect a mobile device.
You’ll also notice that the entire string ends with Edge /12.0, which Chrome does not. There are ways to develop your website to progressively enhance itself based on the availability of features rather than by targeting specific browsers.
Often, lazy developers will just sniff for the UA string and disable content on their website based on which browser they believe the viewer is using. Internet Explorer 8 is a common point of frustration for developers, so they will frequently check if a user is using ANY version of IE, and disable features.
For example, the Modernize library is a fantastic and simple way of detecting features. Over the past year, we’ve seen some UA-sniffing sites that have been updated to detect Microsoft Edge … only to provide it with a legacy IE11 code path.