          models.UUIDField: UUIDField,
          models.GenericIPAddressField: IPAddressField,
          models.FilePathField: FilePathField,
      }
      if postgres_fields:
          serializer_field_mapping[postgres_fields.HStoreField] = HStoreField
          serializer_field_mapping[postgres_fields.ArrayField] = ListField
          serializer_field_mapping[postgres_fields.JSONField] = JSONField
 
</s> remove             (postgres_fields and isinstance(model_field, postgres_fields.JSONField)):
 </s> add             (postgres_fields and isinstance(model_field, postgres_fields.JSONField)) or \
            (hasattr(models, 'JSONField') and isinstance(model_field, models.JSONField)): </s> remove         if postgres_fields and isinstance(model_field, postgres_fields.JSONField):
 </s> add         is_django_jsonfield = hasattr(models, 'JSONField') and isinstance(model_field, models.JSONField)
        if (postgres_fields and isinstance(model_field, postgres_fields.JSONField)) or is_django_jsonfield:
    if hasattr(models, 'JSONField'):
        serializer_field_mapping[models.JSONField] = JSONField
          models.UUIDField: UUIDField,
          models.GenericIPAddressField: IPAddressField,
          models.FilePathField: FilePathField,
      }
    if hasattr(models, 'JSONField'):
        serializer_field_mapping[models.JSONField] = JSONField
      if postgres_fields:
          serializer_field_mapping[postgres_fields.HStoreField] = HStoreField
          serializer_field_mapping[postgres_fields.ArrayField] = ListField
          serializer_field_mapping[postgres_fields.JSONField] = JSONField
keep keep keep add keep keep keep keep
 Add support for Django 3.1 JSONField (#7467)

Django 3.1 adds a new generic JSONField to replace the PostgreSQL-specific one. This adds support for the new field type, which should behave the same as the existing PostgreSQL field.

Django's new JSONField also includes support for a custom "decoder", so add support for that in the serializer field. 
rest_framework/serializers.py