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

Http Request Header User Agent

James Lee
• Saturday, 31 July, 2021
• 15 min read

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.

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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/”.

Your browser sends the user agent to every website you connect to. There is no conventional way of writing an user agent string as different browsers use different formats and many web browsers load a lot of information onto their user agents.

The user agent application is Mozilla version 5.0. The operating system is NT version 10.0 (and is running on a Windows(64-bit) Machine).

Google Chrome Internet Explorer Firefox Safari Opera See your article appearing on the GeeksforGeeks main page and help other Geeks.

Making statements based on opinion; back them up with references or personal experience. An user agent (UA) string is able to be used to detect what version of a specific browser is being used on a certain operating system.

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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.

But this property is not available for Metro Style App in Win8 Consumer Preview. HttpWebRequest is a complete implementation of a HTTP request using raw TCP in .NET.

HTTP .dll but was not handled in user code Additional information: The format of value '”not submitting” to {RFC2616}' is invalid.” These header lines are sent by the client in an HTTP protocol transaction.

In Internet mail format, this gives the name of the requesting user. This field may be used for logging purposes and an insecure form of access protection.

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(For example, when a request is passed through a gateway, then the original issuer's address should be used). This field contains a semicolon-separated list of (Content-Type meta information values) which will be accepted in the response to this request.

See the appendix on the negotiation algorithm as a function and penalty model. Note that a semicolon has a higher precedence than a comma in this syntax, to conform to MIME use.

In order to save time, and also allow clients to receive content types of which they may not be aware, an asterisk “*” may be used in place of either the second half of the content-type value, or both halves. Parameters on the content type are extremely useful for describing resolutions, color depths, etc.

They will allow a client to specify in the Accept: field the resolution of its device. This may allow the server to economize greatly on transmission time by reducing the result ion of an image, for example, and enable a more appropriate custom-designed black and white image to be selected rather than giving the client a color image to convert into monochrome.

Similar to Accept, but lists the Language values which are preferable in the response. This line if present gives the software program used by the original client.

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This is for statistical purposes and the tracing of protocol violations. The first white space delimited word must be the software product name, with an optional slash and version designated.

Other products which form part of the user agent may be put as separate words. This optional header field allows the client to specify, for the server's benefit, the address (URI) of the document (or element within the document) from which the URI in the request was obtained.

This allows a server to generate lists of back-links to documents, for interest, logging, etc. The second word is a username (typically derived from a USER environment variable or prompted for), with an optional password separated by a colon (as in the URL syntax for FTP).

This line if present contains account information for the costs of the application of the method requested. The format of the rest of the line is a function of the charging system, but it is recommended that this includes a maximum cost whose payment is authorized by the client for this transaction, and a cost unit.

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.


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.

^ 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.

An user agent is a string that a browser or application sends to each website you visit. Web servers use this data to assess the capabilities of your computer, optimizing a page’s performance and display.

Ignore the X-Amzn-Trace-Id as it is not sent by Python Requests, instead generated by Amazon Load Balancer used by Hatpin. Any website could tell that this came from Python Requests, and may already have measures in place to block such user agents.

As before lets ignore the headers that start with X- as they are generated by Amazon Load Balancer used by Hatpin, and not from what we sent to the server Although we had set an user agent, the other headers that we sent are different from what the real Chrome browser would have sent.


Let’s add these missing headers and make the request look like it came from a real Chrome browser If you are making many requests for web scraping a website, it is a good idea to randomize.

In order to make your requests from web scrapers look as if they came from a real browser: They have a huge database of the combination of headers that are sent by specific versions of a browser on different operating systems and websites.

Have a Referee header with the previous page you visited or Google, to make it look real There is no point rotating the headers if you are logging in to a website or keeping session cookies as the site can tell it is you without even looking at headers We advise you to use proxy servers when making many requests and use a different IP for each browser or the other way Rotating user agents can help you from getting blocked by websites that use intermediate levels of bot detection, but advanced anti-scraping services has a large array of tools and data at their disposal and can see past your user agents and IP address.

We are not responsible for how it is used and assume no liability for any detrimental usage of the source code. The tutorials only help illustrate the technique of programming web scrapers for popular internet websites.

We are not obligated to provide any support for the code, however, if you add your questions in the comments section, we may periodically address them. Accept-Encoding: GZIP, deflate Permanent RFC2616, 7231 Accept-LanguageList of acceptable human languages for response.

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Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ== Permanent Cache-Control Used to specify directives that must be obeyed by all caching mechanisms along the request -response chain. Cache-Control: no-cache Permanent ConnectionControl options for the current connection and list of hop-by-hop request fields. Must not be used with HTTP /2.

Content-Encoding: GZIP Permanent Content-LengthThe length of the request body in octets (8-bit bytes). Date: Tue, 15 Nov 1994 08:12:31 GMT Permanent ExpectIndicates that particular server behaviors are required by the client.

Expect: 100-continue Permanent ForwardedDisclose original information of a client connecting to a web server through an HTTP proxy. Forwarded: for=;photo= HTTP ;by= for=, for= Permanent Froth email address of the user making the request.

The HTTP2-Settings header field is a connection-specific header field that includes parameters that govern the HTTP /2 connection, provided in anticipation of the server accepting the request to upgrade. If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT Permanent If-None-MatchAllows a 304 Not Modified to be returned if content is unchanged, see HTTP Tag.

If-Range: “737060cd8c284d8af7ad3082f209582d” Permanent If-Unmodified-SinceOnly send the response if the entity has not been modified since a specific time. If-Unmodified-Since: Sat, 29 Oct 1994 19:43:31 GMT Permanent Max-ForwardsLimit the number of times the message can be forwarded through proxies or gateways.

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(The word “referrer” has been misspelled in the RFC as well as in most implementations to the point that it has become standard usage and is considered correct terminology) Referee: HTTP :// Permanent Trailer The Trailer general field value indicates that the given set of header fields is present in the trailer of a message encoded with chunked transfer coding. Trailer: Max-Forwards Permanent Transfer-Encoding The form of encoding used to safely transfer the entity to the user.

Currently, defined methods are: chunked, compress, deflate, GZIP, identity. Upgrade: h2c, HTTPS/1.3, IRC/6.9, RTA/x11, web socket Permanent Misinforms the server of proxies through which the request was sent.

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 a HTTPrequestheader string identifying browser, application, operating system which connects to the server.

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