HTTP Status Codes

HTTP response status codes indicate whether a specific HTTP request has been successfully completed.
They help browsers, APIs, servers, and developers understand the result of an HTTP operation.

Responses are grouped into five main classes, each representing a different range of numbers.

Status Code Categories

1. Informational Responses (100–199)

These codes indicate that the request was received and understood, and that the client should continue.

Common examples:

Use case example:

• Used when large data uploads require confirmation before continuing.

2. Successful Responses (200–299)

These codes indicate that the request was successfully received, understood, and processed.

Common examples:

Use case example:

• API returning user profile → 200 OK
• Creating a new user → 201 Created

3. Redirect Responses (300–399)

These codes tell the client to take further action, often by making a new request.

Common examples:

Use case example:

• Redirecting from http:// to https://
• Redirecting old URLs after a website redesign

4. Client Error Responses (400–499)

These indicate an error caused by the client (bad syntax, invalid credentials, forbidden access, etc.).

Common examples:

Use case example:

• Wrong JSON format → 400
• Missing auth token → 401
• User lacks permissions → 403
• Incorrect API endpoint → 404

5. Server Error Responses (500–599)

These indicate the server failed to fulfill a valid request.

Common examples:

Use case example:

• Database outage → 503
• Reverse proxy error → 502

Full Status Code Diagram

100–199 → Information
200–299 → Success
300–399 → Redirect
400–499 → Client Error
500–599 → Server Error