The difference between PUT and PATCH in APIs lies in how they handle updates to resources:

PUT

• Definition: Replaces the entire resource with the new data provided. If any fields are omitted in the request, they may be reset to their default values or removed.
• Use Case: When you want to update the entire resource or replace it completely.
• Idempotency: PUT requests are idempotent (repeating the same request produces the same result).

Example: Updating a user's profile information.

Request:

PUT /users/1
Content-Type: application/json

{
  "name": "John Doe",
  "email": "john.doe@example.com",
  "phone": "123456789"
}

• If you omit "phone", it might be set to null or removed entirely from the resource.

PATCH

• Definition: Partially updates a resource. Only the fields specified in the request are updated, leaving other fields unchanged.
• Use Case: When you want to modify specific fields of a resource without altering the entire resource.
• Idempotency: PATCH requests are also idempotent, but only update the specified fields.

Example: Updating only the user's phone number.

Request:

PATCH /users/1
Content-Type: application/json

{
  "phone": "0701123123"
}

• Only the phone field is updated; other fields like name and email remain unchanged.

Key Comparison Table

Choosing Between PUT and PATCH

• Use PUT if you need to replace or overwrite the resource.
• Use PATCH for more efficient partial updates, especially for large resources.

By understanding these differences, you can design APIs that better match the expected behavior and resource handling.