HTTP Verbs & Status Codes

Learning objectives

• Recognize the common HTTP methods
• Interpret status codes by class
• Understand safe versus non-safe methods

Common HTTP methods

HTTP defines a set of verbs that describe the intention of a request:

• GET - retrieve a resource, never changes server state
• POST - submit data, such as a contact form
• PUT and PATCH - update a resource
• DELETE - remove a resource

Using the correct verb keeps applications predictable and secure. For example, actions that change data should never be triggered by a GET request, because links and pre-fetchers can repeat them unintentionally.

Reading status codes

• 2xx - Success: 200 OK, 201 Created
• 3xx - Redirection: 301 Moved Permanently, 304 Not Modified
• 4xx - Client error: 404 Not Found, 403 Forbidden
• 5xx - Server error: 500 Internal Server Error, 503 Service Unavailable

Why this matters

When we audit a client platform, the first thing we look at is its response patterns. A flood of 404 responses or a high rate of 500 errors tells a clear story about code quality, configuration, and server health.

Key takeaways

• Use GET for reading and POST for writing.
• Status codes are grouped by class: 2xx, 3xx, 4xx, 5xx.
• Diagnosis starts with reading status codes correctly.