HTTP is the abbreviation for Hypertext Transfer Protocol and is an application protocol to allow communication between physically dispersed systems

It was initially devised by Sir Tim Berners Lee in 1989. The W3C now coordinates it.

In its most basic format, it is what establishes how web pages communicate from the webserver to the user’s browser.

Hypertext is the text that is used on web pages, and that connects one page to another, either within the same system or externally. They are the links that connect the content on the Internet.

How does HTTP work?

HTTP is an application protocol to transfer resources over the Internet.

HTTP uses Port 80, which is the port from which the webserver accepts requests.

Most of the resources are files (images, etc.) but can include other types of data such as scripts.

HTTP sessions are opened by an HTTP client (that is, the user’s browser) through a user agent, and a connection request message is sent to the HTTP server (that is, the webserver). The request message is also known as ‘client request’ and consists of the following lines:

1. Request line
2. Headings
3. Empty string
4. An optional message body
5. Once the response has been delivered, the webserver closes the connection.

This type of connection is known as Stateless. The link only exists for the period of data exchange.
Depending on the availability or not of the resource, HTTP provides an appropriate status code (also known as ‘server response’), determined by the protocol. They are the following:

1. 1xx: a simple informational message
2. 2xx: the success of some kind (ex: 200 OK – file found)
3. 3xx: the client to another URL (ex: 301 moved permanently)
4. 4xx: an error on the client-side (ex: 404 files not found)
5. 5xx: a mistake on the server-side (ex: 500 server error)

Secure HTTP (HTTPS)

There is a safer version of HTTP known as HTTPS. This usually involves the use of an SSL certificate that creates a secure and encrypted connection between the browser and the webserver.

It is usually used in areas of websites where sensitive data is transferred, such as payment details or access credentials. In recent years, HTTPS has become a ranking factor for Google, and more and more websites are moving to HTTPS for that reason.

While HTTP uses Port 80, HTTPS uses 443 for communication.