What is HTTP (Hypertext Transfer Protocol)?

HTTP (Hypertext Transfer Protocol) is an application-layer protocol that enables communication between web clients, such as browsers, and web servers. It defines how clients request resources and how servers respond with the requested content or other information.

When a user visits a website, HTTP allows the browser to request resources such as HTML pages, images, and scripts, which the server then returns in an HTTP response. HTTP also supports communication between web applications and APIs, enabling data to be exchanged between different systems.

How Does HTTP Work?

HTTP operates through a client-server model, enabling web browsers and other clients to communicate with servers over a network. When a user opens a website or interacts with a web application, the client initiates communication with the server hosting the requested resource.

A typical HTTP communication process involves three steps:

1. Request: The client sends an HTTP request to the server to retrieve a resource or perform an action.
2. Processing: The server receives the request and determines how to handle it.
3. Response: The server returns an HTTP response, and the client processes the returned information to display a web page or handle the requested data.

What Are HTTP Requests and Responses?

HTTP requests and responses are messages exchanged between a client and a server. Requests specify the action the client wants to perform, while responses communicate the outcome and return any relevant data.

HTTP Request

An HTTP request typically contains a request method, URL or path, headers, and an optional body.

For example, a browser sends a GET request to retrieve a webpage, while an application may use POST to submit registration details. Request headers provide additional information, such as accepted content formats, authentication credentials, and client preferences.

HTTP Response

An HTTP response contains a status code indicating the outcome, headers providing additional information, and an optional body containing the requested content or other data.

For example, 200 OK indicates success, while 404 Not Found indicates that the requested resource could not be found. The Content-Type response header identifies the media type of the returned content, such as text/html, application/json, or image/jpeg.

Common HTTP Methods and Status Codes

Common HTTP Methods

HTTP methods define the actions a client can perform on a resource, such as retrieving a webpage, submitting data, or updating a resource. Each method specifies the intended operation.

• GET: Retrieves a resource from the server.
• POST: Submits data to the server, often to create a resource or trigger an operation.
• PUT: Creates or replaces a resource at a specified location.
• PATCH: Applies partial updates to a resource.
• DELETE: Requests the removal of a resource.
• HEAD: Retrieves response headers without returning the response body.

Common HTTP Status Codes

An HTTP status code is a three-digit number in an HTTP response that indicates the outcome of a request. Status codes are grouped into five categories, from 1xx (informational) to 5xx (server errors).

• 1xx – Informational: Indicates that the request has been received and processing continues.
• 2xx – Success: Indicates that the request was successfully processed, such as 200 OK or 201 Created.
• 3xx – Redirection: Indicates that further action is required, such as following a redirect.
• 4xx – Client Errors: Indicates a problem with the request, such as 400 Bad Request, 403 Forbidden, or 404 Not Found.
• 5xx – Server Errors: Indicates that the server encountered a problem, such as 500 Internal Server Error or 503 Service Unavailable.

What Is HTTP Used For?

HTTP enables communication across a wide range of online services. Common applications include:

• Website delivery: Transferring HTML, CSS, JavaScript, images, and other webpage resources.
• Web applications: Supporting interactive features, form submissions, and user authentication workflows.
• API communication: Exchanging information between applications and services, often using JSON.
• File transfers: Uploading and downloading documents, images, and other files.
• Streaming and media delivery: Delivering audio, video, and other media content through HTTP-based technologies.

What Is the Difference Between HTTP and HTTPS?

HTTP and HTTPS both enable communication between clients and web servers, but they differ in security and data protection.

How to Improve HTTP Delivery?

Improving HTTP delivery involves caching content closer to users, optimizing dynamic content, adopting modern protocols such as HTTP/2 and HTTP/3, and mitigating malicious traffic that could disrupt service availability.

Providers like CDNetworks combine web performance solutions with Web Application Firewall (WAF) and DDoS protection to improve HTTP delivery performance and protect websites and applications against web application attacks and DDoS attacks.

Explore CDNetworks’ solutions for HTTP delivery and security.

FAQ

Is HTTP a stateless protocol?

HTTP is a stateless protocol, meaning each request is independent, and the protocol does not inherently retain client state between requests. Applications can maintain sessions using mechanisms such as cookies, tokens, and server-side session storage.

What is an example of an HTTP request?

An HTTP request example is GET /index.html HTTP/1.1, which asks a web server to retrieve the /index.html resource.

Can DDoS attacks be launched over HTTP?

HTTP can be used to launch DDoS attacks by sending excessive requests to overwhelm a website or application. HTTP flood attacks are a common example, consuming server resources and disrupting service availability.

Can HTTP be used to transfer files?

HTTP supports file transfers, allowing browsers and applications to upload and download files through HTTP requests and responses.

Does HTTP require a TCP connection?

HTTP does not always require a TCP connection. HTTP/1.1 and HTTP/2 use TCP, while HTTP/3 uses QUIC over UDP instead.