HTML HTTP Messages

Understanding HTTP Messages

HTTP (Hypertext Transfer Protocol) messages are how data is exchanged between your browser and the web server.

They are structured as simple, plain-text messages: Request messages are sent by the browser to fetch resources, and Response messages are returned by the server containing the files.

Example: Understanding HTTP Messages

<!-- Request: GET /index.html HTTP/1.1 -->
<!-- Response: HTTP/1.1 200 OK -->
<a href="/index.html">Home</a>

HTTP Request Headers

HTTP Request headers are metadata fields sent by the browser to tell the server what document type it expects, what browser is being used, or what cookies are saved for the site.

Example: HTTP Request Headers

<!-- Request header: Accept: text/html -->
<!-- Request header: User-Agent: Mozilla/5.0 -->

HTTP Response Headers

HTTP Response headers are metadata fields returned by the server to tell the browser how to handle, cache, and display the returned content securely.

Example: HTTP Response Headers

<!-- Response header: Content-Type: text/html; charset=UTF-8 -->
<meta charset="UTF-8">

Standard HTTP Status Codes

Every HTTP response message includes a standard three-digit status code that informs the browser of the request outcome, grouped into categories: 2xx (Success), 3xx (Redirection), 4xx (Client Error), and 5xx (Server Error).

Example: Standard HTTP Status Codes

<!-- 200 OK, 301 Moved Permanently, 404 Not Found, 500 Server Error -->
<a href="/new-page">301 redirected link</a>

Form Methods and HTTP Messaging

When a user submits an HTML form, the method attribute (GET or POST) defines how the data is packaged inside the HTTP message: GET appends query parameters to the URL path, while POST packages data securely inside the HTTP message body.

Example: Form Methods and HTTP Messaging

<form action="/search" method="get">
  <input type="text" name="q">
</form>
<form action="/login" method="post">
  <input type="password" name="password">
</form>