GET vs POST: Uncover the Real Differences Behind HTTP Requests

GET and POST are the two basic HTTP request methods. The most obvious difference is that GET includes parameters in the URL, while POST sends them in the request body.

Common interview "standard answers" list several practical differences:

GET is harmless when the browser goes back, but POST resubmits the request.

GET URLs can be bookmarked; POST URLs cannot.

GET requests are cached by browsers by default; POST requests are not unless manually configured.

GET supports only URL‑encoding; POST supports multiple encoding types.

GET parameters remain in browser history; POST parameters do not.

GET URLs have length limits (typically ~2 KB); POST has no inherent limit.

GET accepts only ASCII characters; POST imposes no character‑set restriction.

GET is less secure because parameters are exposed in the URL.

GET passes parameters via the URL, POST via the request body.

Both methods rely on the TCP/IP protocol, so at the transport layer they are essentially identical TCP connections. Technically you could send a request body with GET or put parameters in the URL for POST, but HTTP defines specific semantics for each.

Why do the "standard" differences exist? Browsers and servers impose practical limits: most browsers restrict URL length to about 2 KB, and many servers reject URLs larger than 64 KB. Some servers may ignore a GET request body, making it unreliable.

Another key distinction is the TCP packet flow: a GET request sends the HTTP header and data in a single packet exchange, while a POST typically involves two steps—first the header, then the server replies with a 100 Continue, followed by the data packet. This makes POST slightly slower, though the impact is negligible on good networks and can improve reliability on poor connections.

Nevertheless, the semantics of GET (safe, idempotent) and POST (non‑idempotent) should not be mixed arbitrarily, and browser implementations vary (e.g., Firefox may send only one packet for POST).

In summary, GET and POST are fundamentally the same TCP connection, but HTTP rules, browser/server limits, and packet‑level behavior create observable differences in practice.