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

Android Firefox User Agent String

Christina Perez
• Sunday, 22 May, 2022
• 13 min read

Mozilla/5.0 (platform ; RV: gecko version) Gecko/ gecko trail Firefox / firefoxversion Firefox OS phones say Mobile “; the web is the platform.

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Appname / app version indicates the application name and version. Firefoxversion will generally represent the equivalent Firefox release corresponding to the given Gecko version.

When Firefox runs on a device that has the phone form factor, there is a Mobile; token in the platform part of the UA string. The preferred way to target content to a device form factor is to use CSS Media Queries.

For increased interoperability, if the browser is running on a version below 4 it will report 4.4. Starting in Version 6, users can opt into using a GeckoView-based Focus for Android with a hidden preference: it uses a GeckoView UA string to advertise Gecko compatibility.

Klein Version (Rendering Engine) UserAgentstring 1.0 (Review)Mozilla/5.0 (Linux; Android 7.0) Apple WebKit/537.36 (HTML, like Gecko) Version/4.0 Klein/1.0 Chrome/58.0.3029.83 Mobile Safari/537.364.1+ (Review)Mozilla/5.0 (Linux; Android 7.0) Apple WebKit/537.36 (HTML, like Gecko) Version/4.0 Focus/4.1 Chrome/62.0.3029.83 Mobile Safari/537.366.0+ (GeckoView)Mozilla/5.0 (Android 7.0; Mobile; RV:62.0) Gecko/62.0 Firefox /62.0 Version 7 of Focus for iOS uses an useragentstring with the following format: Note: this user agent was retrieved from an iPhone XR simulator and may be different on device.

Some of them we have noticed are of the form Nelson; “, Reopen; “, or Open C; (note that putting space is also discouraged). Firefox OS version numberGecko version number1.'s easy to find the correspondences by looking at the Mercurial repository names : repositories starting by mozilla-b2g are the release repositories for Firefox OS, and have both Firefox OS and Gecko versions in their names.

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The first two digits are owned by the Mozilla product team and denote versions with new features (e.g.: v1.1, 1.2, etc). The third digit is incremented with regular version tags (about every 6 weeks) for security updates, and the fourth is owned by the OEM.

Identifier preferences, (see the obsolete Sergeant Strings Reference). In the past, specific plug-ins, add-ons or extensions added user agent parts to notify sites they were installed.

The recommended way to do this, if it's absolutely necessary (remember that it slows down every request) is to set a custom HTTP header. Making statements based on opinion; back them up with references or personal experience.

To do so, simply visit our project on the Debate hosted instance, create an account and either select an existing language or add a new one to get going. This way it becomes much easier for me to keep track of reported issues and get back to you if additional information is needed to help you.

While all phones come with pre-installed browsers, both Google Play and Apple App Store offer a number of alternative browsers, some focusing on speed and lightness, others on saving bandwidth and blocking ads, and an ever-increasing amount claiming to increase privacy and reduce a users' mobile digital footprint. Feel free to browse the stats for your local market using our Data Explorer tool.

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Choose the string that you need from a preset list (or from custom entries) with the Sergeant Switcher extension. Once you add the extension to Firefox you can access the alternate useragentstring in two ways.

Note: The useragentstring will automatically reset back to the default each time you restart Firefox. You can create, edit, and delete current user agent strings or use the import/export functions.

The Sergeant Switcher extension provides a quick and easy way to change the useragentstring for those less than cooperative websites. For those wanting to add additional user agent strings visit this website (available in XML file format).

She has previously written under the pen name “Asian Angel” and was a Life hacker intern before joining How-To Geek/Lifesaver Media. Updated 2014-04-28: Reader G. pointed out that this feature is no longer supported.

Extra: * To check your current user agent, enter about: in the URL * To revert your changes, right-click on general.user agent.override. If you're not familiar with web development, browsers have continuously updated their user agent strings to become longer, to maintain compatibility with websites and minimize end- user impact.

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First, it wants to 'freeze' the useragentstring, meaning the contents will no longer stay up-to-date (as removing it entirely would cause countless websites to cease working). Chrome 83, currently slated for release in June, will freeze the browser and OS versions in the string.

Diego Android App Updated To Version 2.0 With New Features And UI Changes That Bring It Into The Post-Gingerbread Era 2013/12/24 1:39pm PST Dec 24, 2013 While web applications really shouldn't use them to determine what features of a page will be delivered to the agent, they are one of the few resources available for administrators of websites to understand where their traffic is coming from.

The administrators review new unclassified strings that have enough usage to be interesting and write rules that classify them. This is a problem that I don't feel is really manageable by pure curation or parsing rules though.

Many times the UA string will have dozens of tokens describing different capabilities and characteristics of the mobile device. Our existing rules based UA parsing system that I wrote a few years back is busted.

I believe that an ML approach could provide a strong baseline that would be able to categorize and classify both existing user agent strings and ones that haven't come into existence yet, giving a confidence score that can be used to determine whether that classification should be used in analysis. I would like to see an open source project that could take a UA string and parse the following attributes out of it.

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Not required but UA should be included with requests Used for statistical purposes, tracing protocol violations tailoring responses to user agent limitations Field can contain multiple “product tokens” and comments Product tokens are listed in order of significance for identifying the application It’s interesting to note that, even in this RFC, it already warns of anomalies like some proxies will append data to the UA which makes interpretation ambiguous, and some clients don’t follow the product token syntax.

So, in theory, you could shove emoji or a base64 essay into the UA, but all bets are off on how the server decides if and how to handle it. What’s notable is the addition of very specific prohibitions against putting non-essential, fine-grained information or advertising in the UA.

But as the other browsers caught to Mozilla in terms of features, web designers were slow (or didn’t bother) to update their serving rules to match. This is most likely what prompted the latest RFCs to specifically say using another product’s string (i.e. Mozilla) is discouraged.

What you’ll also notice is that every browser is fairly idiosyncratic with the sequence and types of product tokens it has. With enough study you can fairly reliably know what device and browser a request is coming from.

This usage is the original intended purpose of the UA string, giving the server the ability to serve different versions of the web page based on what the client is capable of handling. Internet Explorer 6 was perhaps the most egregious example of where site designers needed to know the browser version because of how poorly it handled modern web standards.

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Fun side note, IE6 was a HUGE problem in the late 2000s/early 2010s due to its horrible standards support requiring lots of custom hacks from developers but stubbornly high usage numbers. Using JavaScript to pull browser info was still in its infancy, so User -Agents were the most informative thing that you had.

In practice, this method only really works on the tiny subset of people who have installed enough browser extensions or poorly spoofed their UA enough to stand out from the crowd of default strings. But even so, the UA still provides bits of entropy in a larger user fingerprinting framework that involves the use of JavaScript and HTML5 methods.

With many advanced browser features being detected directly via JavaScript these days, this is probably the primary modern use of the UA string, figuring out what device/platform a client is running. While UAS used to tell you what percent of your user base was on IE, Firefox or Chrome on a Windows machine or Mac, we suddenly started seeing exciting new strings like iPad, iPhone, Android.

Running (up to) a thousand regex searches on a single string is obviously very resource-intensive, but this is the only way to make sure to identify a UA string to the fullest extent possible short of reading it manually. In practice, you can speed up things massively with hashing and caching by relying on the fact that most users will have the same general default setup, so you’d only have to run regex on novel strings.

Often this is thinking from a mix of outdated thinking from a decade ago when people often only had 1 internet-connected computer, or they’ve heard about browser fingerprinting but aren’t aware of how many data points it takes to fingerprint a browser. I’ve personally had to use UAS to put very rough bounds on the minimum number of browsers used to view a site, with the raw hit count being the upper limit.

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When people hear that UA scan be spoofed easily, they often worry that they’re being lied to and their metrics are going to be off. The primary reason is that the vast majority of users have no motivation to bother messing with their UA string.

The only people who want to manipulate their UA are usually a microscopic number of users writing bots/crawlers of some sort. Out of hundreds, thousands, possibly millions of humans using your site every day, they’re ultimately insignificant because they represent such a fractional percent of traffic.

So long as they’re generally well-behaved and low volume, they won’t skew your metrics much so you can ignore it like the above. There are often signs of problems (like your systems overloading like it’s a DDoS attack) when you’re facing these sorts of bots.

It’s pretty rare to have to worry about spoofing unless you’re running something that robot-makers have an incentive to abuse (and UA is not likely to be the solution if that’s your problem). I suppose there are some edge cases: like if you get practically no traffic, so the bots will dominate, but you also have little reason to do a lot of analytics at that point.

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