Networking

HTTP (HyperText Transfer Protocol) is a protocol that enables data exchange between a client (browser) and a server. Every time you open a webpage or send a request to an API, HTTP is used.

Essential Parts of HTTP:

Request: contains the method, URL, headers, and optionally a body.
Response: contains the status code, headers, and the body with the data.

HTTP Methods

HTTP methods define what action the client wants to perform on the server.

Common Methods:

GET — retrieve data. Used to load pages or fetch API data.
POST — create or send data to the server. Used when submitting forms or creating resources.
PUT — fully replace an existing resource.
PATCH — partially update a resource.
DELETE — remove a resource.
OPTIONS — check which methods and headers the server supports (often used in CORS preflight).

HTTP Status Codes

Status codes inform the client about the result of the request.

1xx — informational (e.g., 100 Continue)
2xx — success (200 OK, 201 Created)
3xx — redirection (301 Moved Permanently, 302 Found)
4xx — client errors (400 Bad Request, 401 Unauthorized, 404 Not Found)
5xx — server errors (500 Internal Server Error)

HTTP Headers

Headers are metadata sent along with a request or response.

Request Headers:

Content-Type — type of data sent by the client.
Accept — type of data the client can handle.
Authorization — tokens or credentials.
Cache-Control — caching rules.

Response Headers:

Content-Type — type of data returned.
Set-Cookie — stores session information.
Cache-Control — caching rules for the client.

CORS (Cross-Origin Resource Sharing)

What is CORS: a browser security mechanism that controls access to resources from different origins.

Why frontend developers face issues:

Browsers block requests to another domain unless the server explicitly allows it via the Access-Control-Allow-Origin header.
Before the main request, the browser may send a preflight request with the OPTIONS method.

Tips:

Configure the server or proxy to allow CORS for trusted domains.
Use proper caching headers (Cache-Control) to improve performance.