What is Hypertext Transfer Protocol (HTTP)?

Ever wondered how machines talk to each other on the internet? How are you able to access your favourite websites? Web Protocols are the answer. Web protocols are the standards that dictate the rules that machines use to communicate over the web to send and receive files. They lay the foundation for your experience on the web, and understanding how they work will improve your own website’s user experience and security.

When you type a URL into your browser and press Enter, protocols are working silently to communicate with the servers to get you the HTML document for that website. 

In this blog, we will discuss HTTP protocol, its components, request, response, status code, and much more. Let’s get started.

Table of Contents:

• What is HTTP Protocol?
• How HTTP Works
• What are HTTP Methods?
• What are HTTP request headers?
• What are HTTP Response Headers?
• What are HTTP Status Codes?
• HTTP vs HTTPS Protocol
• HTTP/2 and HTTP/3 – Modern Protocol Enhancements
• HTTP and Web Security Concerns
• Advantages and Limitations of HTTP
• Where Does HTTP Operate in the OSI Stack?

What is HTTP Protocol?

HTTP stands for HyperText Transfer Protocol. It is an application-layer protocol used for transmitting hypertext (like HTML documents) across the Internet. When you try to access a URL on your machine, your browser sends an HTTP request to the server, which responds with the requested HTML document. This document contains all the information required to display the website on your machine, including CSS files, scripts, and/or multimedia content.

How HTTP Works

Let’s demystify the purpose of the HTTP protocol and take a closer look at what is happening under the hood:

Client-Server Communication Flow

The client-server communication flow is the core foundation of how the HTTP protocol in computer networks works. 

• The client (your web browser) initiates a request.
• The server (machine hosting the website) receives the request, processes it, and sends back a response.

HTTP is a stateless protocol, meaning each request is an independent transaction that uses a protocol stack. 

Protocol Stack (TCP/IP, QUIC)

• TCP (Transmission Control Protocol): Used by previous versions like HTTP/2 but still ensures reliable and ordered delivery of data.

• QUIC (Quick UDP Internet Connections): First introduced in HTTP/3 runs over UDP and provides faster and more secure connections. 

Life of an HTTP Transaction

Let’s walk through a typical HTTP transaction:

1. A URL is entered into your browser.
2. The domain name is converted into an IP address with DNS resolution.
3. A connection is established between the browser and server with either TCP or QUIC.
4. The browser sends an HTTP request to the server.
5. The server processes the request and sends a response that includes the HTML document that you require.
6. The browser processes the response and renders the website.

This process can repeat multiple times for additional assets like images, stylesheets, scripts, etc.

These HTTP transactions are made up of methods, body, and status codes. Understanding each component is crucial to making a successful transaction. Let’s start with the methods.

What are HTTP Methods?

HTTP methods define an action that is to be performed. This tells the server what kind of action you are trying to perform.

HTTP GET Method

The GET Method is used to request data from a server at a specified resource (usually a URL). When you visit a webpage or click a link, you’re typically making a GET request.

If you are trying to apply a filter to a website, the GET request would ideally look like:

GET /products?category=laptops&max_price=50000 HTTP/1.1
Host: www.techmart.in

HTTP POST Method

The POST method is used to send data to the server to create a new resource. It’s commonly used in form submissions and APIs. For instance, submitting a registration form to /register with user details like name, email, and password is a POST request.

Example:

POST /register
Body:
{
  "name": "Aditi",
  "email": "[email protected]",
  "password": "secure123"
}

HTTP PUT Method

The PUT method is used to update an existing resource. It replaces the entire content of the specified resource. If you update a user profile by sending a request to /users/101 with new information, you are using a PUT request.

Example:

PUT /users/101
Body:
{
  "name": "Aditi Sharma",
  "email": "[email protected]"
}

HTTP DELETE Method

The DELETE method, as the name suggests, is used to remove a resource from the server. If you want to delete a product from a database, you might send a DELETE request to /products/55.

Example:

DELETE /products/55

HTTP HEAD Method

The HEAD method is similar to GET but retrieves only the headers of a resource, not the body. It’s useful when you want to check if a file or resource exists (like an image) without downloading it. For example, a HEAD /images/logo.png request might be used by a browser or crawler to fetch metadata.

Example:

HEAD /images/logo.png

HTTP OPTIONS Method

The OPTIONS method is used to determine what HTTP methods are supported by a server or specific endpoint. It’s often used in CORS (Cross-Origin Resource Sharing) scenarios. A request to OPTIONS /api/users might return something like Allow: GET, POST, PUT, indicating the allowed actions.

What are HTTP request headers?

• Headers provide additional information about the request to the server, which can include browser type and what response formats you can accept. This facilitates a clean transaction.
• The body contains the actual data that is being sent.

Example:

POST /submit-form HTTP/1.1
Host: example.com
Content-Type: application/json
{ "name": "Intellipaat", "email": "[email protected]" }

What are HTTP Response Headers?

Response headers contain the details about the server’s response, which can include how the content should be cached, the type of server, and the format of the response so that your browser can read and process it efficiently.

Status codes show the outcome of the request, whether it was successful, redirected, or resulted in an error.

Example:

HTTP/1.1 200 OK
Content-Type: text/html
Cache-Control: no-cache

What are HTTP Status Codes?

HTTP status codes signify the outcome of a request. They contain 3 digits and help both developers and browsers understand whether a request was successful, redirected, or encountered an error. They help developers troubleshoot faster and identify the exact issue that is being faced.

1. Informational (1xx)

These codes state that a request was received and is being processed.

2. Success (2xx)

The request was successfully received, understood, and accepted by the server.

3. Redirection(3xx)

The client needs to take further action to complete the request.

4. Client Errors (4xx)

There was a problem with the request.

5. Server Errors (5xx)

The client has failed to process a valid request.

These codes play a critical role in debugging and search optimization by clearly defining the issue.

HTTP vs HTTPS Protocol

What is HTTPS?

HTTPS stands for Hypertext Transfer Protocol Secure. As you can tell from the name, it is a more secure version of HTTP. It is used when a more secure and encrypted connection is required for sensitive information like login credentials, financial information, etc. You can identify that an HTTPS connection is being used from the padlock icon next to the address bar in your browser.

Key Differences: Encryption, Security, SSL/TLS

Here are some of the key differences between HTTPS and HTTP:

The core protocol behavior doesn’t change; the only difference is that all communication is wrapped in encryption via SSL/TLS. This means that the methods, headers, and status codes stay the same.

HTTP/2 and HTTP/3 – Modern Protocol Enhancements

HTTP/2 

The HTTP/2 protocol was introduced in 2015. It made several changes to increase the loading speed of websites.

• Multiplexing: Allows multiple requests to be sent over a single connection simultaneously.
• Header Compression: Compression of the data in the header makes it smaller and faster.
• Server Push: Allows the server to send additional data to the browser before it is requested.
• Stream Prioritization: Allows critical resources (like CSS or fonts) to load before others.
• Binary Protocol: Transmits data in binary instead of text, making it faster to parse.

HTTP/3 

HTTP/3, first released in 2022, builds further on HTTP/2 by using QUIC, a transport protocol developed by Google that runs over UDP instead of TCP.

HTTP and Web Security Concerns

While HTTP is a critical aspect of web communications, it is important to understand the security limitations it comes with. It is inherently insecure because the data is transmitted in plain text. Malicious hackers can make use of this vulnerability to intercept your request and steal sensitive information if you’re not careful. This is the reason HTTPS was created and is used to transfer sensitive data. It uses SSL/TLS to encrypt the data, making it more secure. Let’s explore the potential vulnerabilities in detail.

1. Man-in-the-Middle (MITM) Attacks

Hackers can intercept and alter communication between the browser and the server, especially over public Wi-Fi.

2. Eavesdropping

Anyone monitoring an HTTP connection can read all the information being exchanged.

3. Session Hijacking

Without encryption, attackers can steal session cookies and impersonate users.

Advantages and Limitations of HTTP

HTTP, like any other tool or concept in programming, comes with various advantages and disadvantages. You should critically evaluate your use case before implementing it. Let’s have a look at some advantages and disadvantages of using HTTP in your code.

Where Does HTTP Operate in the OSI Stack?

The Application Layer of the OSI model is where the HTTP protocol functions. The OSI model is a conceptual framework that standardizes how data is transmitted over the Internet. It consists of seven layers, ranging from the physical transmission of signals to the final application-level interaction. Let’s explore each layer in a little more detail.

Frequently Asked Questions