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 Vs Client

Ava Flores
• Thursday, 17 December, 2020
• 14 min read

If it lives on the device or in the browser, it's a public client. What type of client you have, determines which OAuth grants to use.



On public clients, you cannot have the client itself authenticate with the authorization server (only the user is authenticated) and therefore you can't get refresh tokens from the authorization server. Example: Suppose you have a slideshow app (the client) on your iPad that wants to access your Flickr photos.

If that app asked you (the resource owner) to provide your Flickr credentials so that it can access your photos, then you, being a security-wise user, would not do so: you have no idea what that app might do with your credentials. Luckily, rather than asking for your credentials, it instead brings forward your iPad browser (your user agent), which you trust, to login to Flickr.

You sleep well at night knowing that the slideshow app did not take your credentials and do something naughty with them. The whole point of the protocol is that users should not trust arbitrary applications with their credentials.

The protocol requires users to understand this to be effective. Client | agent | is that client is (computing) the role of a computer application or system that requests and/or consumes the services provided by another having the role of server while agent is (computing) in the client -server model, the part of the system that performs information preparation and exchange on behalf of a client or server especially in the phrase “intelligent agent it implies some kind of autonomous process which can communicate with other agents to perform some collective task on behalf of one or more humans.

(en noun) A customer, a buyer or receiver of goods or services. *, title=(The Celebrity), chapter=8, passage=I corralled the judge, and we started off across the fields (legal) A person who employs or retains an attorney to represent him or her in any legal matter, or one who merely divulges confidential matters to an attorney while pursuing professional assistance without subsequently retaining the attorney.

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Heaven made us agents, free to good or ill. --Dryden. One who acts for, or in the place of, another (the principal), by authority from him; one entrusted with the business of another; a substitute; a deputy; a factor.

I see in him outrageous strength, with an inscrutable malice sine wing it. Especially in the phrase “intelligent agent it implies some kind of autonomous process which can communicate with other agents to perform some collective task on behalf of one or more humans.

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. Let's talk about how the Accept-CH and Sec-CH-UA-* headers will work, how you can test that with your own services today, and what comes next.

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It's been supported in Chrome on desktop & Android since 2015, and other Chromium-based browsers, though it's not yet available in Firefox or Safari. Until now, it's been used to request bonus details from browsers, such as the user's connection speed, viewport size or screen density.

The exact lifetime is left up to the client (a previous draft included an Accept-CH-Lifetime header, but that's now been removed) but it's likely to be at least the rest of the current browser session. All of this is Chrome only right now, although there's some progress in other browsers, and the standardization process is intended to encourage that.

The set of opt-in hints supported in the latest stable Chrome includes: This is a general prefix for a forbidden header name as defined by the Fetch spec.

In addition to potential data transfer concerns (especially for HTTP/1.1 clients or servers), requesting too much information may trip a privacy budget or otherwise trigger permission prompts in the future, and implies collecting unnecessary personal information about your users. The draft also proposes a navigator.userAgentData JavaScript API to access this hint data client -side, but that doesn't seem to be implemented anywhere yet.

Right now, the only browser that supports this is Chrome, and only in the dev & canary channels, and behind a flag. That said, testing it out now allows you to see how this might impact your application, and start to see how you can capture any hints that you need to handle this, once this does land for real.

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Safari haven't formally announced their position, but they've previously attempted to freeze the UA in preview builds (though that was partially rolled back), and it seems likely they'd follow suit once the rest of the ecosystem commits to this. Watch out for more changes in the same direction too, as browsers move other finger printable data behind client hints in the future, including the Accept-Language header, and begin investigating approaches like GREASE to mitigate sniffing risks.

You can follow the detailed progress on this in the Chromium and Firefox bug trackers. Accept-CH in general is now in its last call for comments, until the 8th of May 2020, whilst the UA freezing and client hints details are still very much subject to change, with discussion happening in the Wing UA- client -hints repo on GitHub.

See your article appearing on the GeeksforGeeks main page and help other Geeks. User agent refers to the application that remotely accesses a different computer, usually a server, through the network.

It means that the Web browser you're using is accessing a program (such as Gmail) or a service (such as that operates on some other faraway computer. Your computer (the client) is connecting to the desired Web page (the server) through one of the TCP/IP protocols.

When you key in a “query” on your Web browser (user agent) and hit “enter,” a text string (a programming sequence of symbols) is sent to the server of that website. While the text string identifies itself to the server as an user agent, it simultaneously requests access to the website.

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When the Internet was young, the World Wide Web was dominated by a few of the first generation of browsers. As a result, many Web servers were designed to interact and connect with only those leading browsers.

This was possible because the website could identify that Web browser as the user agent by its text string when it requested access to the site. To overcome this roadblock, competing browsers were modified to replicate or impersonate text strings that would be accepted by the website.

An early example of this is when the browser Internet Explorer spoofed its primary rival at the time, Netscape Navigator. They did it so people using Internet Explorer could gain access to websites that were being limited to Netscape browser users.

Rv: gecko version indicates the release version of Gecko (such as 17.0 “). The Chrome (or Chromium/Blink-based engines) user agent string is similar to Firefox’s.

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/”.

oauth2 oauth agent flow user tutorial learn wikitechy programs examples

Essentially, an user agent is a way for a browser to say “Hi, I’m Mozilla Firefox on Windows” or “Hi, I’m Safari on an iPhone” to a web server. The user agent string identifies the browser as IE 9 with the Trident 5 rendering engine.

The plot thickens: Chrome is pretending to be both Mozilla and Safari. To understand why, we’ll have to examine the history of user agents and browsers.

(Yes, this means that you can sometimes bypass registration screens by setting your user agent to Google bot.) He's written about technology for nearly a decade and was a World columnist for two years.

Chris has written for The New York Times, been interviewed as a technology expert on TV stations like Miami's NBC 6, and had his work covered by news outlets like the BBC. Since 2011, Chris has written over 2,000 articles that have been read more than 500 million times---and that's just here at How-To Geek.

During the first browser war, many web servers were configured to send web pages that required advanced features, including frames, to clients that were identified as some version of Mozilla only. Other browsers were considered to be older products such as Mosaic, Cello, or Samba, and would be sent a bare-bones HTML document.

user agents spoofing

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 user agent string 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. 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 user agent string. 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.

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^ a b RFC 3261, SIP: Session Initiation Protocol, IETF, The Internet Society (2002) ^ RFC 7231, Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content, IETF, The Internet Society (June 2014) ^ Net news Article Format. 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. ^ “Chrome Phasing out Support for User Agent ".

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