What is HTTP?

HTTP (HyperText Transfer Protocol) is an application-layer protocol used to exchange data between a client and a server over the internet.

In simpler terms: HTTP is a set of rules that let a browser and a server "talk" to each other.

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#Why HTTP is needed

HTTP is needed so that:

• a browser can request a web page
• a server can send a response
• the client and the server understand each other

Without HTTP, a browser would not know:

• how to ask for a page
• how the server should respond
• how to tell whether the request succeeded

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#Where HTTP is used

HTTP is used almost everywhere:

• when opening websites
• in REST APIs
• in mobile applications
• when services exchange data with each other

Every time you:

• visit a site
• click a button
• submit a form

, HTTP is at work.

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#How HTTP works (simplified)

1. A client (for example, a browser) sends an HTTP request
2. The server accepts the request
3. The server processes it
4. The server sends an HTTP response
5. The client receives and uses the result

The model is always the same: request, response

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#What data is transferred over HTTP

HTTP can transfer:

• HTML pages
• JSON and XML
• images
• files
• form data

HTTP does not care what exactly is being transferred, it just delivers the data.

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#Important properties of HTTP

#1. Application layer

HTTP runs at the application layer of the OSI model and relies on the lower layers (TCP/IP) to deliver data.

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#2. Stateless

HTTP is a stateless protocol:

• the server does not store the client's state
• every request is independent
• all the necessary information is passed in the request

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#3. Text-based and readable

HTTP requests and responses:

• have a clear structure
• are easy to read and debug
• are convenient for development and testing

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#A real-life example

When you type in a site's address:

• the browser sends an HTTP request: "give me the page"
• the server replies with an HTTP response: "here is the page and status 200 OK"
• the browser shows the page to the user

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#Short answer for an interview

Remember this phrasing:

HTTP is an application-layer protocol that defines the rules for exchanging data between a client and a server, and it is used to transfer web pages and API requests over the internet.