What is the difference between PUT and POST methods?

The key differences between PUT and POST are:

PUT:

• Idempotent: Multiple identical requests have the same effect
• Specific target: Usually targets a specific resource with known identifier
• Replace/Create: Replaces entire resource or creates if doesn't exist
• Safe to retry: Can be safely retried without side effects

POST:

• Not idempotent: Multiple requests may have different effects
• Collection target: Usually targets a collection to create new resources
• Create/Process: Creates new resources or processes data
• Not safe to retry: May create duplicate resources if retried

Examples:

PUT /users/123     # Replace/update user 123 specifically
POST /users        # Create a new user (server assigns ID)