HTTP Header Parser

Paste raw HTTP headers below to parse and analyze them. Instantly see header names and values for debugging and development.

HTTP Header Analysis

HTTP headers are metadata sent with web requests and responses. They control caching, authentication, content types, and much more. This tool parses header strings into readable key-value pairs.

Paste headers from browser dev tools, curl output, or API logs. The parser breaks them down and explains what each header does.

Common Headers

  • Content-Type: What kind of data (HTML, JSON, etc.)
  • Authorization: Authentication credentials
  • Cache-Control: Caching instructions
  • Set-Cookie: Cookie storage

Understanding HTTP Headers

HTTP headers are key-value pairs sent between clients and servers that provide essential metadata about the request or response. They control everything from content type and encoding to caching behavior, authentication, and security policies. Understanding headers is fundamental for web developers, API designers, and security professionals.

Headers are divided into request headers (sent by the client), response headers (sent by the server), and general headers (applicable to both). Each header serves a specific purpose, and proper configuration can significantly impact your website's performance, security, and functionality.

Common HTTP Headers Explained

  • Content-Type:Specifies the media type of the resource (e.g., text/html, application/json)
  • Cache-Control:Directives for caching mechanisms in both requests and responses
  • Authorization:Contains credentials for authenticating the user agent with a server
  • User-Agent:Identifies the client software making the request
  • Accept:Media types that are acceptable for the response
  • Content-Length:The size of the message body in bytes
  • Set-Cookie:Server sends cookies to the user agent

Security-Related Headers

  • Content-Security-Policy (CSP):Prevents XSS attacks by controlling resource loading
  • Strict-Transport-Security (HSTS):Forces HTTPS connections
  • X-Frame-Options:Prevents clickjacking by controlling iframe embedding
  • X-Content-Type-Options:Prevents MIME type sniffing attacks
  • X-XSS-Protection:Enables browser's built-in XSS filtering

Debugging with HTTP Headers

Analyzing HTTP headers is essential for troubleshooting web applications. Headers reveal why resources aren't caching properly, why authentication is failing, or why security policies are blocking content. Browser developer tools, command-line tools like curl, and specialized proxy software can capture headers for analysis. Our parser helps you quickly format and understand raw header data, making debugging faster and more efficient.

Frequently Asked Questions

How do I view HTTP headers in my browser?

Open browser DevTools (F12), go to the Network tab, make a request, and click on it to see headers. You can also use curl with the -I flag to view response headers from the command line.

What are the most important security headers?

Content-Security-Policy (CSP), Strict-Transport-Security (HSTS), X-Content-Type-Options, and X-Frame-Options are critical for web security. These headers prevent XSS attacks, force HTTPS, prevent MIME sniffing, and stop clickjacking.

Why do headers matter for performance?

Cache-Control and ETag headers control caching behavior, reducing server load and improving load times. Proper caching headers can dramatically speed up repeat visits by allowing browsers to use cached resources instead of re-downloading.

How do I set custom headers?

In web servers like Apache or Nginx, use configuration directives. In programming, use functions like PHP's header() or JavaScript's fetch() options. API tools like Postman let you add custom headers for testing and development purposes.