django-rest-framework/docs/api-guide/metadata.md

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---
source:
- metadata.py
---
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# Metadata
> [The `OPTIONS`] method allows a client to determine the options and/or requirements associated with a resource, or the capabilities of a server, without implying a resource action or initiating a resource retrieval.
>
> — [RFC7231, Section 4.3.7.][cite]
REST framework includes a configurable mechanism for determining how your API should respond to `OPTIONS` requests. This allows you to return API schema or other resource information.
There are not currently any widely adopted conventions for exactly what style of response should be returned for HTTP `OPTIONS` requests, so we provide an ad-hoc style that returns some useful information.
Here's an example response that demonstrates the information that is returned by default.
HTTP 200 OK
Allow: GET, POST, HEAD, OPTIONS
Content-Type: application/json
{
"name": "To Do List",
"description": "List existing 'To Do' items, or create a new item.",
"renders": [
"application/json",
"text/html"
],
"parses": [
"application/json",
"application/x-www-form-urlencoded",
"multipart/form-data"
],
"actions": {
"POST": {
"note": {
"type": "string",
"required": false,
"read_only": false,
"label": "title",
"max_length": 100
}
}
}
}
## Setting the metadata scheme
You can set the metadata class globally using the `'DEFAULT_METADATA_CLASS'` settings key:
REST_FRAMEWORK = {
'DEFAULT_METADATA_CLASS': 'rest_framework.metadata.SimpleMetadata'
}
Or you can set the metadata class individually for a view:
class APIRoot(APIView):
metadata_class = APIRootMetadata
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def get(self, request, format=None):
return Response({
...
})
The REST framework package only includes a single metadata class implementation, named `SimpleMetadata`. If you want to use an alternative style you'll need to implement a custom metadata class.
## Creating schema endpoints
If you have specific requirements for creating schema endpoints that are accessed with regular `GET` requests, you might consider re-using the metadata API for doing so.
For example, the following additional route could be used on a viewset to provide a linkable schema endpoint.
@action(methods=['GET'], detail=False)
def api_schema(self, request):
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meta = self.metadata_class()
data = meta.determine_metadata(request, self)
return Response(data)
There are a couple of reasons that you might choose to take this approach, including that `OPTIONS` responses [are not cacheable][no-options].
---
# Custom metadata classes
If you want to provide a custom metadata class you should override `BaseMetadata` and implement the `determine_metadata(self, request, view)` method.
Useful things that you might want to do could include returning schema information, using a format such as [JSON schema][json-schema], or returning debug information to admin users.
## Example
The following class could be used to limit the information that is returned to `OPTIONS` requests.
class MinimalMetadata(BaseMetadata):
"""
Don't include field and other information for `OPTIONS` requests.
Just return the name and description.
"""
def determine_metadata(self, request, view):
return {
'name': view.get_view_name(),
'description': view.get_view_description()
}
Then configure your settings to use this custom class:
REST_FRAMEWORK = {
'DEFAULT_METADATA_CLASS': 'myproject.apps.core.MinimalMetadata'
}
# Third party packages
The following third party packages provide additional metadata implementations.
## DRF-schema-adapter
[drf-schema-adapter][drf-schema-adapter] is a set of tools that makes it easier to provide schema information to frontend frameworks and libraries. It provides a metadata mixin as well as 2 metadata classes and several adapters suitable to generate [json-schema][json-schema] as well as schema information readable by various libraries.
You can also write your own adapter to work with your specific frontend.
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If you wish to do so, it also provides an exporter that can export those schema information to json files.
[cite]: https://tools.ietf.org/html/rfc7231#section-4.3.7
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[no-options]: https://www.mnot.net/blog/2012/10/29/NO_OPTIONS
[json-schema]: https://json-schema.org/
[drf-schema-adapter]: https://github.com/drf-forms/drf-schema-adapter