HTTPS
Hypertext Transfer Protocol Secure (HTTPS) is an extension of the Hypertext Transfer Protocol (HTTP) for secure communication over a computer network, and is widely used on the Internet. In HTTPS, the communication protocol is encrypted using Transport Layer Security (TLS), or, formerly, its predecessor, Secure Sockets Layer (SSL). The protocol is therefore also often referred to as HTTP over TLS, or HTTP over SSL.
World Wide Web
The following example demonstrates the functioning of a web browser when accessing a page at the URL codice_1. The browser resolves the server name of the URL (codice_2) into an Internet Protocol address using the globally distributed Domain Name System (DNS). This lookup returns an IP address such as "203.0.113.4" or "2001:db8:2e::7334". The browser then requests the resource by sending an HTTP request across the Internet to the computer at that address. It requests service from a specific TCP port number that is well known for the HTTP service, so that the receiving host can distinguish an HTTP request from other network protocols it may be servicing. The HTTP protocol normally uses port number 80 and for HTTPS protocol it normally is port number 443. The content of the HTTP request can be as simple as two lines of text:
The computer receiving the HTTP request delivers it to web server software listening for requests on port 80. If the web server can fulfil the request it sends an HTTP response back to the browser indicating success:
followed by the content of the requested page. HyperText Markup Language (HTML) for a basic web page might look like this:
The web browser parses the HTML and interprets the markup (, for paragraph, and such) that surrounds the words to format the text on the screen. Many web pages use HTML to reference the URLs of other resources such as images, other embedded media, scripts that affect page behaviour, and Cascading Style Sheets that affect page layout. The browser makes additional HTTP requests to the web server for these other Internet media types. As it receives their content from the web server, the browser progressively renders the page onto the screen as specified by its HTML and these additional resources.