What Does Your User Agent Say About You?


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.

The user agent string can be accessed with JavaScript on the client side using the navigator.userAgent property.

A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".


User Agent String

Browser Data

User Agent String Operating System

Ava Flores
• Monday, 28 December, 2020
• 18 min read

As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion.

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The second link under PHP in my list also contains basically the same information which is simple enough that you should be able to translate it to any language. Keep in mind that using the user agent for anything is rife with problems.

Unless you're willing to dedicate a portion of your development time to monitoring user agents visiting your site and performing constant maintenance, you should try to avoid doing it entirely. Then you also need to account for OSes released for phones, tablets, gaming consoles, clocks, etc which can have much more frequent release cycles and unpredictable changes in market share.

Just look at how BlackBerry, Palm OS, Web OS, iOS, Android, Windows Mobile, and Windows Phone have changed market share in just the last few years to name a few. Unless the operating system is a dependency of your site, like if you're creating a targeted “download” page for an app (which in itself can be rife with problems), it is almost always better to use feature detection, which will allow you to future-proof your development without having to constantly maintain browser or OS detection code.

It's worth keeping in mind that the user agent header can easily be faked. If you want to send the client a response specific to its environment you should perhaps distinguish differences from content-type or encoding.

The Sergeant from the browser is not something I would rely on for anything, We all use it for statistics, but we know they're not 100% accurate. Great, but extremely elaborate: you'll probably want to re-think the project you need the list for, since this one puts 'things in perspective'.

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Rv: gecko version indicates the release version of Gecko (such as 17.0 “). For compatibility, it adds strings like HTML, like Gecko and Safari.

The Opera browser is also based on the Blink engine, which is why it almost looks the same, but adds “Or/”. In this example, the useragentstring is mobile Safari’s version.

Platform identifiers change based on the operating system being used, and version numbers also increment as time passes. 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. Mozilla/5.0 (compatible; bingo/2.0; + BrowserBingBotVersion2.0Browser maker Microsoft Corporation Operating system unknowns versionunknownFaked user agent NoCrawlerYesDevice typeunknownPointerunknown When you request a Web page, your browser sends (user agent request) a number of headers to the server hosting the site that you are visiting.

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Mozilla/5.0 : Previously used to indicate compatibility with the Mozilla rendering engine. (HTML, like Gecko) : Browser platform details.

By convention the word “bot” is included in the name of the agent. 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 useragentstring 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.

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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 useragentstring.

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. Following the lifting of export restrictions, most vendors supported 256-bit encryption.

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.

You may have reached us looking for answers to questions like: How to find the useragentstring. So, to get info about your browser, websites often examine the ‘ user agent ’, or ‘UA’ string.

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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.

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.

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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. People use user agent sniffing to detect if the users' device is touch-friendly and has a small screen, so they can optimize their website accordingly.

While user agent sniffing can sometimes detect these, not all devices are the same: some mobile devices have big screened sizes, some desktops have a small touchscreen, some people use smart TV's which are an entirely different ballgame altogether, and some people can dynamically change the width and height of their screen by flipping their tablet on its side! 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.

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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). Always be very deliberate about choosing the right media query and choosing the right >=, , >, or < in any corresponding JavaScript because it is very easy to get these mixed up, resulting on the website looking working right at the screen size where the layout changes.

One such case is using user agent sniffing as a fallback when detecting if the device has a touch screen. Internet Explorer (on Windows) and WebKit (on iOS) are two perfect examples.

However, Internet Explorer was such a special little wasp exception prior to version 9 that it was very easy to detect the browser based upon the browser-specific features available. 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.

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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) 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 UserAgentString EdgeHTMLEdge/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 OperatingSystem is given in most Sergeant strings (although not web-focused platforms like Firefox OS), but the format varies a lot.

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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. If the device is large enough that it's not marked with “Mob”, you should serve your desktop site (which, as a best practice, should support touch input anyway, as more desktop machines are appearing with touchscreens).

Web-sniffer n/a Collage n/a webs n/a Fuzz n/a What Web n/a Gunpowder n/a WkHTMLtoPDF WebKit WordPress ping back n/a Yahoo Ad monitoring n/a Yandex. Translate n/a Yea link client n/a Yours n/a NameLayout engine n/a Mobiles n/a Mr.4×3 Powered n/a. When a host is infected or otherwise compromised, security professionals need to quickly review packet captures (caps) of suspicious network traffic to identify affected hosts and users.

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This tutorial offers tips on how to gather that cap data using Wireshark, the widely used network protocol analysis tool. In most cases, alerts for suspicious activity are based on IP addresses.

If you have access to full packet capture of your network traffic, a cap retrieved on an internal IP address should reveal an associated MAC address and hostname. DHCP traffic can help identify hosts for almost any type of computer connected to your network.

Open the cap in Wireshark and filter on boot pas shown in Figure 1. Note : With Wireshark 3.0, you must use the search term DHCP instead of boot.

Select one of the frames that shows DHCP Request in the info column. Go to the frame details section and expand the line for Bootstrap Protocol (Request) as shown in Figure 2.

Expand the lines for Client Identifier and Host Name as indicated in Figure 3. Client Identifier details should reveal the MAC address assigned to 172.16.1[.

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With HTTP-based web browsing traffic from a Windows host, you can determine the operating system and browser. This cap is from an Android host using an internal IP address at

A quick Google search reveals this model is an LG Phoenix 4 Android smartphone. This cap is from an iPhone host using an internal IP address at 10.0.0114.

Figure 11: Following the TCP stream for an HTTP request in the fifth cap However, for those lucky enough to find HTTP web-browsing traffic during their investigation, this method can provide more information about a host.

Other Articles You Might Be Interested In

01: Screen Reader User Agent
02: Parse User Agent Javascript
03: Parsing User Agent String
04: Mobile Edge Browser User Agent
05: Mobile Phone User Agent
06: Mobile User Agent Regex
07: Modify User Agent Javascript
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