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Non Breaking Changes

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What is a NON Breaking Change?

1. Adding a new optional field in request or response body.
2. Changing field from mandatory to optional in request or response body.
3. Adding a new endpoint.
4. Performance improvements.
5. Adding new enum values to the request body.

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What is a Breaking Change?

1. Removing or renaming things.
   // before
   { "userId": 42 }
   // after
   { "id": 42 }
   
2. Changing data types.
   // before
   { "age": 30 }
   // after
   { "age": "30" }
   
3. Making optional things required.
   // before, deliveryTime optional
   POST /orders
   { "note": "call me" }
   // after, deliveryTime required
   POST /orders
   { "note": "call me", "deliveryTime": "18:00" }
   
4. Changing response status code. I.e. from 404 to 400.
5. Changing behavior or meaning.
   1. Same endpoint, different logic.
   2. Same field, different interpretation.