Anatomy of an HTTP request

HTTP is just text

Once the TCP connection from unit 3 is open, the browser speaks HTTP (HyperText Transfer Protocol). The surprise for most beginners: an HTTP request is plain, readable text. That fact is worth the whole unit: because requests are text, you can read them in debugging tools, write them by hand, and reason about them directly — no decompiling, no magic. Here is a complete real one:

GET /about HTTP/1.1
Host: example.com
User-Agent: Mozilla/5.0

Three parts, always in this order:

1. Request line: METHOD PATH VERSION. Here: the method GET ("give me"), the path /about, and the protocol version.
2. Headers: one Name: value per line. Extra information about the request. Host says which site you want (one server can host many sites), User-Agent says what kind of client is asking.
3. A blank line, which means "headers are done". Requests that upload data (like form submissions) put a body after the blank line. A GET has no body.

On the wire each line ends with the two characters \r\n (carriage return + newline), a detail you will see again when reading raw traffic.