HTTP headers are key-value pairs sent with every HTTP request and response to convey metadata about the communication. They play a critical role in defining how data is handled between client and server.

Common Header Fields 📋

  • Accept
    Specifies the types of content the client is willing to receive.

    Accept
    [Learn more about `Accept` headers](/en/http_headers/accept)

  • Content-Type
    Indicates the media type of the request/response body.

    Content_Type
    [Explore `Content-Type` examples](/en/http_headers/content_type)

  • User-Agent
    Identifies the client's software, OS, and browser.

    User_Agent
    [Check `User-Agent` formats](/en/http_headers/user_agent)

  • Authorization
    Contains credentials for server authentication.

    Authorization
    [Read about security headers](/en/http_headers/security)

Key Concepts 🔍

  • Headers are case-insensitive but typically written in lowercase.
  • They are separated by CRLF (Carriage Return LineFeed) in raw HTTP.
  • Custom headers can be added for specific use cases (e.g., X-Requested-With).

Tools for Inspection 🛠

  • Use browser developer tools to view headers in network requests.
  • Commands like curl -I show headers without the response body.
  • View a header example to see how they work in practice.

For deeper understanding, check our guide on HTTP methods or request lifecycle.