In a REST API, a response header is a part of the HTTP response that contains additional information about the response.
The headers are key-value pairs that provide additional context about the response, such as the type of content returned, the date and time the response was generated, the caching directives, and more.
Some common response headers used in REST APIs include:
- Content-Type: Indicates the type of content in the response body, such as “application/json” for JSON data.
- Content-Length: Specifies the size of the response body in bytes.
- Date: Indicates the date and time the response was generated.
- ETag: A unique identifier for the current version of the resource, used for caching.
- Location: The URL of the newly created resource when a POST request is successful.
- Link: URLs related to the resource in the response.
- Allow: Indicates which HTTP methods are supported by the resource.
These headers provide important information to the client, allowing them to properly handle and process the response.
Additionally, some headers can also be used to control the caching of the response, to optimize the performance of the API.