Status Codes

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HTTP Status Codes Demystified

Understand request success, errors, and redirection patterns through standardized HTTP status codes.

1. Status Code Categories

1xx - Informational

Request received, continuing process.

2xx - Success

Request completed successfully.

3xx - Redirection

Further action required to complete request.

4xx - Client Error

Malformed request syntax or unresolvable semantics.

5xx - Server Error

Server failed to fulfill valid request.

2. Common Status Codes

Code Phrase Context
200 OK Successful request
400 Bad Request Malformed request syntax
401 Unauthorized Missing/invalid credentials
403 Forbidden Valid auth, but no perms
404 Not Found No resource exists
500 Internal Server Error Unexpected server condition

3. Status Code Examples

Success


HTTP/1.1 201 Created
Location: /new-resource/abc123
Content-Type: application/json

{ "id": "abc123", "status": "active" }

Error


HTTP/1.1 409 Conflict
Content-Type: application/problem+json

{ 
  "error": "InvalidOperation", 
  "message": "Duplicate resource ID"
}

4. Response Lifecycle

Status Flow

Request
→ 200 OK

Client-Server Interaction

Client sends: GET /data
Server responds: 304 Not Modified
Client retries: GET /data@if-modified-since
Server delivers: 200 OK with content