HTTP Header Reference

Overview

# HTTP Header Reference

HTTP headers are an essential part of communication between web browsers, servers, APIs, and other HTTP clients. They provide additional information about requests and responses, including content type, caching, authentication, security, and browser behavior.

What Are HTTP Headers?

HTTP headers are key-value pairs sent with an HTTP request or response. They help the client and server understand how to process the exchanged data.

For example:

Content-Type: application/json

This header tells the client that the response contains JSON data.

Common HTTP Request Headers

- Accept — Specifies the content types the client can process. - Authorization — Sends authentication credentials or tokens. - Content-Type — Specifies the format of the request body. - User-Agent — Identifies the client making the request. - Referer — Indicates the page that led to the current request.

Common HTTP Response Headers

- Content-Type — Specifies the format of the response. - Content-Length — Indicates the size of the response body. - Cache-Control — Controls browser and intermediary caching. - Set-Cookie — Sends cookies to the client. - Location — Specifies a redirect or resource location. - Content-Encoding — Indicates how the response content is encoded.

HTTP Security Headers

Security-related headers can help protect websites against common browser-based attacks.

Examples include:

- Content-Security-Policy - Strict-Transport-Security - X-Content-Type-Options - Referrer-Policy - Permissions-Policy

Why HTTP Headers Matter

Understanding HTTP headers is useful when developing websites, REST APIs, authentication systems, web applications, and debugging network requests. Inspecting headers can also help identify caching, security, redirect, and content-delivery issues.

Conclusion

This HTTP Header Reference provides a convenient starting point for understanding commonly used HTTP headers and their roles in web communication. Developers can use it when building, testing, and troubleshooting websites and APIs.