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

Python Requests Header User Agent

Danielle Fletcher
• Sunday, 22 May, 2022
• 29 min read

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 PythonRequests, instead generated by Amazon Load Balancer used by Hatpin. Any website could tell that this came from PythonRequests, 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.

These pieces of information, referred to as headers, are intended to make communications on the web easier and more reliable, as the server has a better idea of how to respond. Well, a lot of companies set up their servers in a way that allows them to identify the browser a client is using.

In fact, most websites may look a tiny bit different in Chrome, Firefox, Safari and so on. Based on the browser, a specific version of the web page is sent to the client for optimal visual and computational performance.

A more serious issue arises when the server decides to block all unrecognized traffic. In that case, to continue scraping, we need to provide a legitimate user agent.

Fortunately, all browsers’ user agent strings are available publicly on the internet. For instance, suppose we want to make a GET request to YouTube, pretending to be a client using Chrome.

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In our case, we have saved the dictionary in the ‘ header variable, so we pass that to the parameter. Well, an HTTP cookie is a special type of request header that represents a small piece of data sent from a website and stored on the user ’s computer.

Cookies were designed to be a reliable mechanism for websites to remember stateful information, such as items added in the shopping cart in an online store, or to record the user ’s browsing activity. They can also be used to remember arbitrary pieces of information that the user previously entered into form fields, such as names, addresses, passwords, and credit-card numbers.

Cookies perform essential functions in the modern web. This basically means that you are not required to sign in every time you open or reload a page.

Cookies are implemented a bit different from the ‘ user agent ’, as websites usually tell us how to set them the first time we visit a page. Despite that, the awesome ‘ requests package saves the day once again with its session class.

You have now added the request headers weapon to your web scraping arsenal. The course is part of the 365 Data Science Program. You can explore the curriculum or sign up 12 hours of beginner to advanced video content for free by clicking on the button below.


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.

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/”.


In this example, the user agent string is mobile Safari’s version. The Session object allows you to persist certain parameters across requests.

It also persists cookies across all requests made from the Session instance, and will use urllib3 ’s. A Session object has all the methods of the main Requests API.

Sessions can also be used to provide default data to the request methods. Any dictionaries that you pass to a request method will be merged with the session-level values that are set.

This will make sure the session is closed as soon as the with block is exited, even if unhandled exceptions occurred. Whenever a call is made to requests .get() and friends, you are doing two major things.

Here is a simple request to get some very important information from Wikipedia’s servers: In some cases you may wish to do some extra work to the body or headers (or anything else really) before sending a request.


However, the above code will lose some advantages of having a Requests Session object. When you are using the prepared request flow, keep in mind that it does not take into account the environment.

This can cause problems if you are using environment variables to change the behavior of requests. For example: Self-signed SSL certificates specified in REQUESTS _CA_BUNDLE will not be taken into account.

This list of trusted CAS can also be specified through the REQUESTS _CA_BUNDLE environment variable. Note that when verify is set to False, requests will accept any TLS certificate presented by the server, and will ignore hostname mismatches and/or expired certificates, which will make your application vulnerable to man-in-the-middle (Mite) attacks.

If you specify a wrong path or an invalid cert, you’ll get a Error: This allows for users to update their trusted certificates without changing the version of Requests.

This is because Requests may attempt to provide the Content-Length header for you, and if it does this value will be set to the number of bytes in the file. Errors may occur if you open the file in text mode.

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To send a chunk-encoded request, simply provide a generator (or any iterator without a length) for your body: In an ideal situation you’ll have set stream=True on the request, in which case you can iterate chunk-by-chunk by calling iter_content with a chunk_size parameter of None.

This is because Requests may attempt to provide the Content-Length header for you, and if it does this value will be set to the number of bytes in the file. Errors may occur if you open the file in text mode.

Any hooks you add will then be called on every request made to the session. A Session can have multiple hooks, which will be called in the order they are added.

You override this default certificate bundle by setting the standard curl_ca_bundle environment variable to another file path: This is an optional feature that requires that additional third-party libraries be installed before use.

Once you’ve installed those dependencies, using a SOCKS proxy is just as easy as using an HTTP one: Using the scheme socks5 causes the DNS resolution to happen on the client, rather than on the proxy server.


This is in line with curl, which uses the scheme to decide whether to do the DNS resolution on the client or proxy. Requests is intended to be compliant with all relevant specifications and RFCs where that compliance will not cause difficulties for users.

Request provides access to almost the full range of HTTP verbs: GET, OPTIONS, HEAD, POST, PUT, PATCH and DELETE. The following provides detailed examples of using these various verbs in Requests, using the GitHub API.

HTTP GET is an idempotent method that returns a resource from a given URL. As a result, it is the verb you ought to use when attempting to retrieve data from a web location.

An example usage would be attempting to get information about a specific commit from GitHub. We can take advantage of the Requests OPTIONS verb to see what kinds of HTTP methods are supported on the URL we just used.

Turns out GitHub, like many API providers, don’t actually implement the OPTIONS method. If GitHub had correctly implemented OPTIONS, however, they should return the allowed methods in the headers, e.g.


OK, so let’s tell this Kenneth guy that we think this example should go in the quick start guide instead. Request makes it easy to use many forms of authentication, including the very common Basic Auth.

Happily, GitHub allows us to use another HTTP verb, PATCH, to edit this comment. Now, just to torture this Kenneth guy, I’ve decided to let him sweat and not tell him that I’m working on this.

Utilizing this, you can make use of any method verb that your server allows. Transport Adapters provide a mechanism to define interaction methods for an HTTP service.

This adapter provides the default Requests interaction with HTTP and HTTPS using the powerful urllib3 library. Request enables users to create and use their own Transport Adapters that provide specific functionality.

Once created, a Transport Adapter can be mounted to a Session object, along with an indication of which web services it should apply to. The mount call registers a specific instance of a Transport Adapter to a prefix.

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Once mounted, any HTTP request made using that session whose URL starts with the given prefix will use the given Transport Adapter. Many of the details of implementing a Transport Adapter are beyond the scope of this documentation, but take a look at the next example for a simple SSL use- case.

The Requests team has made a specific choice to use whatever SSL version is default in the underlying library (urllib3). You can use Transport Adapters for this by taking most of the existing implementation of HTTPAdapter, and adding a parameter ssl_version that gets passed-through to urllib3.

We’ll make a Transport Adapter that instructs the library to use SSLv3: With the default Transport Adapter in place, Requests does not provide any kind of non-blocking IO.

If you are concerned about the use of blocking IO, there are lots of projects out there that combine Requests with one of Python ’s synchronicity frameworks. By default, requests do not time out unless a timeout value is set explicitly.

It’s a good practice to set connect timeouts to slightly larger than a multiple of 3, which is the default TCP packet retransmission window. (Specifically, it’s the number of seconds that the client will wait between bytes sent from the server.


Urllib.request module uses HTTP/1.1 and includes Connection:close header in its HTTP requests. This actually only works for HTTP, HTTPS and FTP connections.

If context is specified, it must be a SSL.Context instance describing the various SSL options. The optional ca file and CAPASH parameters specify a set of trusted CA certificates for HTTPS requests.

This function always returns an object which can work as a context manager and has the properties URL, headers, and status. For HTTP and HTTPS URLs, this function returns a HTTP.client.HTTPResponse object slightly modified.

Note that None may be returned if no handler handles the request (though the default installed global uses to ensure this never happens). Proxy handling, which was done by passing a dictionary parameter to Ellis.reopen, can be obtained by using objects.

The default opener raises an auditing event Ellis. Request with arguments Fuller, data, headers, method taken from the request object. Changed in version 3.2: HTTPS virtual hosts are now supported if possible (that is, if SSL.HAS_SNI is true).

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The code does not check for a real, and any class with the appropriate interface will work. Handler s can be either instances of, or subclasses of (in which case it must be possible to call the constructor without any parameters).

A subclass may also change its handler_order attribute to modify its position in the handlers list. Urllib.request.get proxies () This helper function returns a dictionary of scheme to proxy server URL mappings.

This is because that variable can be injected by a client using the “Proxy:” HTTP header. If you need to use an HTTP proxy in a CGI environment, either use ProxyHandler explicitly, or make sure the variable name is in lowercase (or at least the _proxy suffix).

For an HTTP POST request method, data should be a buffer in the standard application/x-www-form-urlencoded format. The Ellis.parse.encode() function takes a mapping or sequence of 2-tuples and returns an ASCII string in this format.

This is the host name or IP address of the original request that was initiated by the user. An unverifiable request is one whose URL the user did not have the option to approve.

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Subclasses may indicate a different default method by setting the attribute in the class itself. The request will not work as expected if the data object is unable to deliver its content more than once (e.g. a file or an iterable that can produce the content only once) and the request is retried for HTTP redirects or authentication.

Changed in version 3.3: argument is added to the Request class. Changed in version 3.4: Default may be indicated at the class level.

Changed in version 3.6: Do not raise an error if the Content-Length has not been provided and data is neither None nor a bytes object. The default is to read the list of proxies from the environment variables _proxy.

If no proxy environment variables are set, then in a Windows environment proxy settings are obtained from the registry’s Internet Settings section, and in a Mac OS X environment proxy information is retrieved from the OS X System Configuration Framework. The no_proxy environment variable can be used to specify hosts which shouldn’t be reached via proxy; if set, it should be a comma-separated list of hostname suffixes, optionally with :port appended, for example,,

Class Ellis.request.HTTPPasswordMgr Keep a database of (realm, uri)(user,password) mappings. Class Ellis.request.HTTPPasswordMgrWithDefaultRealm Keep a database of (realm, uri)(user,password) mappings.

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Can be used by a Basically handler to determine when to send authentication credentials immediately instead of waiting for a 401 response first. Password_mgr, if given, should be something that is compatible with ; refer to section HTTPPasswordMgr Objects for information on the interface that must be supported.

If passwd_mgr also provides is_authenticated and update_authenticated methods (see), then the handler will use the is_authenticated result for a given URI to determine whether to send authentication credentials with the request. Password_mgr, if given, should be something that is compatible with ; refer to section HTTPPasswordMgr Objects for information on the interface that must be supported.

HTTPBasicAuthHandler will raise a ValueError when presented with a wrong Authentication scheme. Password_mgr, if given, should be something that is compatible with ; refer to section HTTPPasswordMgr Objects for information on the interface that must be supported.

Password_mgr, if given, should be something that is compatible with ; refer to section HTTPPasswordMgr Objects for information on the interface that must be supported. Password_mgr, if given, should be something that is compatible with ; refer to section HTTPPasswordMgr Objects for information on the interface that must be supported.

This Handler method will raise a ValueError when presented with an authentication scheme other than Digest or Basic. Changed in version 3.3: Raise ValueError on unsupported Authentication Scheme.


Password_mgr, if given, should be something that is compatible with ; refer to section HTTPPasswordMgr Objects for information on the interface that must be supported. The following methods describe Request ’s public interface, and so all may be overridden in subclasses.

It also defines several public attributes that can be used by clients to inspect the parsed request. The URI authority, typically a host, but may also contain a port separated by a colon.

Request.unverifiable boolean, indicates whether the request is unverifiable as defined by RFC 2965. Return whether the instance has the named header (checks both regular and redirected).

Request.set_proxy (host, type) Prepare the request by connecting to a proxy server. The following methods are searched, and added to the possible chains (note that HTTP errors are a special case).

Arguments, return values and exceptions raised are the same as those of reopen() (which simply calls the open() method on the currently installed global). The timeout feature actually works only for HTTP, HTTPS and FTP connections).


The HTTP protocol is a special case which uses the HTTP response code to determine the specific error handler; refer to the http_error_() methods of the handler classes. The order in which these methods are called within each stage is determined by sorting the handler instances.

Handlers with a method named like _open() are called to handle the request. Objects provide a couple of methods that are directly useful, and others that are meant to be used by derived classes.

Barehanded.HTTP_error_default (req, FP, code, msg, hers) This method is not defined in, but subclasses should override it if they intend to provide a catch-all for otherwise unhandled HTTP errors. This method is also not defined in, but will be called, if it exists, on an instance of a subclass, when an HTTP error with code NNN occurs.

Subclasses should override this method to handle specific HTTP errors. Response will be an object implementing the same interface as the return value of reopen().

Some HTTP redirections require action from this module’s client code. HTTPRedirectHandler.redirect_request (req, FP, code, msg, hers, newer) Return a Request or None in response to a redirect.


This is called by the default implementations of the HTTP_error_30*() methods when a redirection is received from the server. The default implementation of this method does not strictly follow RFC 2616, which says that 301 and 302 responses to POST requests must not be automatically redirected without confirmation by the user.

In reality, browsers do allow automatic redirection of these responses, changing the POST to a GET, and the default implementation reproduces this behavior. HTTPRedirectHandler.HTTP_error_301 (req, FP, code, msg, hers) Redirect to the Location: or URI: URL.

This method is called by the parent when getting an HTTP ‘moved permanently’ response. HTTPRedirectHandler.HTTP_error_302 (req, FP, code, msg, hers) The same as, but called for the ‘found’ response.

HTTPRedirectHandler.HTTP_error_303 (req, FP, code, msg, hers) The same as, but called for the ‘see other’ response. HTTPRedirectHandler.HTTP_error_307 (req, FP, code, msg, hers) The same as, but called for the ‘temporary redirect’ response.

This password manager extends to support tracking URIs for which authentication credentials should always be sent. HTTPPasswordMgrWithPriorAuth.is_authenticated (self, author) Returns the current state of the is_authenticated flag for the given URI.

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HTTPBasicAuthHandler.HTTP_error_401 (req, FP, code, msg, hers) Retry the request with authentication information, if available. ProxyBasicAuthHandler.HTTP_error_407 (req, FP, code, msg, hers) Retry the request with authentication information, if available.

HTTPDigestAuthHandler.HTTP_error_401 (req, FP, code, msg, hers) Retry the request with authentication information, if available. ProxyDigestAuthHandler.HTTP_error_407 (req, FP, code, msg, hers) Retry the request with authentication information, if available.

HTTPHandler.HTTP_open (req) Send an HTTP request, which can be either GET or POST, depending on req.has_data(). HTTPSHandler.HTTPS_open (req) Send an HTTPS request, which can be either GET or POST, depending on req.has_data().

Changed in version 3.2: This method is applicable only for local hostnames. But even though some browsers don’t mind about a missing padding at the end of a base64 encoded data URL, this implementation will raise an ValueError in that case.

For 200 error codes, the response object is returned immediately. For non-200 error codes, this simply passes the job on to the http_error_() handler methods, via.


Eventually, will raise an Terror if no other handler handles the error. This is because there is no way for reopen to automatically determine the encoding of the byte stream it receives from the HTTP server.

In general, a program will decode the returned bytes object to string once it determines or guesses the appropriate encoding. As the python .org website uses utf-8 encoding as specified in its meta tag, we will use the same for decoding the bytes object.

In the following example, we are sending a data-stream to the Stein of a CGI and reading the data it returns to us. Note that this example will only work when the Python installation supports SSL.

For example, the http_proxy environment variable is read to obtain the HTTP proxy’s URL. Also, remember that a few standard headers (, and) are added when the Request is passed to reopen() (or).

The following functions and classes are ported from the Python 2 module Ellis (as opposed to urllib2). If the URL points to a local file, the object will not be copied unless filename is supplied.


The third argument, if present, is a callable that will be called once on establishment of the network connection and once after each block read thereafter. The third argument may be -1 on older FTP servers which do not return a file size in response to a retrieval request.

The following example illustrates the most common usage scenario: The data argument must be a bytes object in standard application/x-www-form-urlencoded format; see the Ellis.parse.encode() function.

You can still retrieve the downloaded data in this case, it is stored in the content attribute of the exception instance. If no Content-Length header was supplied, retrieve can not check the size of the data it has downloaded, and just returns it.

Urllib.request.cleanup () Cleans up temporary files that may have been left behind by previous calls to. Unless you need to support opening objects using schemes other than HTTP:, ftp:, or file:, you probably want to use.

By default, the URL opener class sends a header of Ellis/AVV, where AVV is the Ellis version number. Its default value is None, in which case environmental proxy settings will be used if present, as discussed in the definition of reopen(), above.


Additional keyword parameters, collected in x509, may be used for authentication of the client when using the HTTPS: scheme. URL opener objects will raise an Error exception if the server returns an error code.

Open_unknown (Fuller, data=None) Override interface to open unknown URL types. If report hook is given, it must be a function accepting three numeric parameters: A chunk number, the maximum size chunks are read in and the total size of the download (-1 if unknown).

It will be called once at the start and after each chunk of data is read from the network. Version Variable that specifies the user agent of the opener object.

Subclasses URL opener providing default handling for the following HTTP response codes: 301, 302, 303, 307 and 401. For the 30x response codes listed above, the header is used to fetch the actual URL.

For the 30x response codes, recursion is bounded by the value of the max tries attribute, which defaults to 10. For all other response codes, the method http_error_default() is called which you can override in subclasses to handle the error appropriately.

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According to the letter of RFC 2616, 301 and 302 responses to POST requests must not be automatically redirected without confirmation by the user. In reality, browsers do allow automatic redirection of these responses, changing the POST to a GET, and Ellis reproduces this behavior.

The default implementation asks the users for the required information on the controlling terminal. A subclass may override this method to support more appropriate behavior if needed.

The class offers one additional method that should be overloaded to provide the appropriate behavior: The return value should be a tuple, (user,password), which can be used for basic authentication.

The implementation prompts for this information on the terminal; an application should override this method to use an appropriate interaction model in the local environment. Currently, only the following protocols are supported: HTTP (versions 0.9 and 1.0), FTP, local files, and data URLs.

Changed in version 3.4: Added support for data URLs. The reopen() and functions can cause arbitrarily long delays while waiting for a network connection to be set up.

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This means that it is difficult to build an interactive Web client using these functions without using threads. This may be binary data (such as an image), plain text or (for example) HTML.

The code handling the FTP protocol cannot differentiate between a file and a directory. This can lead to unexpected behavior when attempting to read a URL that points to a file that is not accessible.

If the URL ends in a /, it is assumed to refer to a directory and will be handled accordingly. But if an attempt to read a file leads to a 550 error (meaning the URL cannot be found or is not accessible, often for permission reasons), then the path is treated as a directory in order to handle the case when a directory is specified by a URL but the trailing / has been left off.

This can cause misleading results when you try to fetch a file whose read permissions make it inaccessible; the FTP code will try to read it, fail with a 550 error, and then perform a directory listing for the unreadable file.

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