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+# HTTP Cookies
+
+## Cookie overview
+
+  Cookies are `name=contents` pairs that a HTTP server tells the client to
+  hold and then the client sends back those to the server on subsequent
+  requests to the same domains and paths for which the cookies were set.
+
+  Cookies are either "session cookies" which typically are forgotten when the
+  session is over which is often translated to equal when browser quits, or
+  the cookies aren't session cookies they have expiration dates after which
+  the client will throw them away.
+
+  Cookies are set to the client with the Set-Cookie: header and are sent to
+  servers with the Cookie: header.
+
+  For a very long time, the only spec explaining how to use cookies was the
+  original [Netscape spec from 1994](https://curl.haxx.se/rfc/cookie_spec.html).
+
+  In 2011, [RFC6265](https://www.ietf.org/rfc/rfc6265.txt) was finally
+  published and details how cookies work within HTTP. In 2016, an update which
+  added support for prefixes was
+  [proposed](https://tools.ietf.org/html/draft-ietf-httpbis-cookie-prefixes-00),
+  and in 2017, another update was
+  [drafted](https://tools.ietf.org/html/draft-ietf-httpbis-cookie-alone-01)
+  to deprecate modification of 'secure' cookies from non-secure origins. Both
+  of these drafs have been incorporated into a proposal to
+  [replace](https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-02)
+  RFC6265. Cookie prefixes and secure cookie modification protection has been
+  implemented by curl.
+
+## Cookies saved to disk
+
+  Netscape once created a file format for storing cookies on disk so that they
+  would survive browser restarts. curl adopted that file format to allow
+  sharing the cookies with browsers, only to see browsers move away from that
+  format. Modern browsers no longer use it, while curl still does.
+
+  The netscape cookie file format stores one cookie per physical line in the
+  file with a bunch of associated meta data, each field separated with
+  TAB. That file is called the cookiejar in curl terminology.
+
+  When libcurl saves a cookiejar, it creates a file header of its own in which
+  there is a URL mention that will link to the web version of this document.
+
+## Cookies with curl the command line tool
+
+  curl has a full cookie "engine" built in. If you just activate it, you can
+  have curl receive and send cookies exactly as mandated in the specs.
+
+  Command line options:
+
+  `-b, --cookie`
+
+  tell curl a file to read cookies from and start the cookie engine, or if it
+  isn't a file it will pass on the given string. -b name=var works and so does
+  -b cookiefile.
+
+  `-j, --junk-session-cookies`
+
+  when used in combination with -b, it will skip all "session cookies" on load
+  so as to appear to start a new cookie session.
+
+  `-c, --cookie-jar`
+
+  tell curl to start the cookie engine and write cookies to the given file
+  after the request(s)
+
+## Cookies with libcurl
+
+  libcurl offers several ways to enable and interface the cookie engine. These
+  options are the ones provided by the native API. libcurl bindings may offer
+  access to them using other means.
+
+  `CURLOPT_COOKIE`
+
+  Is used when you want to specify the exact contents of a cookie header to
+  send to the server.
+
+  `CURLOPT_COOKIEFILE`
+
+  Tell libcurl to activate the cookie engine, and to read the initial set of
+  cookies from the given file. Read-only.
+
+  `CURLOPT_COOKIEJAR`
+
+  Tell libcurl to activate the cookie engine, and when the easy handle is
+  closed save all known cookies to the given cookiejar file. Write-only.
+
+  `CURLOPT_COOKIELIST`
+
+  Provide detailed information about a single cookie to add to the internal
+  storage of cookies. Pass in the cookie as a HTTP header with all the details
+  set, or pass in a line from a netscape cookie file. This option can also be
+  used to flush the cookies etc.
+
+  `CURLINFO_COOKIELIST`
+
+  Extract cookie information from the internal cookie storage as a linked
+  list.
+
+## Cookies with javascript
+
+  These days a lot of the web is built up by javascript. The webbrowser loads
+  complete programs that render the page you see. These javascript programs
+  can also set and access cookies.
+
+  Since curl and libcurl are plain HTTP clients without any knowledge of or
+  capability to handle javascript, such cookies will not be detected or used.
+
+  Often, if you want to mimic what a browser does on such web sites, you can
+  record web browser HTTP traffic when using such a site and then repeat the
+  cookie operations using curl or libcurl.