1xx Informational

Definition

HTTP status codes ranging from 100-199. They indicate that the request was received and the process is continuing. They are purely informational and rarely interacted with directly by standard frontend developers.

Explain Like I'm New

The server saying: 'Hold on, I heard you, I'm working on it, please wait.'

Real World Example

`101 Switching Protocols`: A client asks the server to upgrade a standard HTTP connection into a persistent WebSocket connection. The server replies with 101 to say 'Okay, we are now speaking WebSockets.'

Common Use Cases

•WebSockets
•Protocol upgrades

Terminal Output

bash / terminal

/* Conceptual Flow of a 101 Switching Protocols (WebSocket Upgrade) 1. Client sends request to connect: GET /chat HTTP/1.1 Upgrade: websocket Connection: Upgrade 2. Server accepts the upgrade: HTTP/1.1 101 Switching Protocols Upgrade: websocket Connection: Upgrade 3. The HTTP connection is kept permanently open and binary data begins flowing. */

Interview Questions

basic

Do you frequently write code to handle 1xx status codes in standard React applications?

intermediate

What does the `100 Continue` status code tell the client?

Flash Cards

Question

Handle in React?

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Answer

No. 1xx codes are handled at the absolute lowest network layers by the browser or the `fetch` API under the hood.

Question

What is 100 Continue?

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Answer

It tells the client that the initial part of a massive request (like the headers of a 5GB file upload) has been received and accepted, and the client should continue sending the rest of the massive body.