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# Global configuration

> Specify global headers, path parameters or query parameters meant to be included on every request.

Fern Definition isn't recommended for new customers and Fern isn't accepting feature requests for this format. It remains supported for existing users.

The `api.yml` configuration supports global configuration like headers and path parameters.

## Global headers

You can specify headers that are meant to be included on every request:

#### api.yml

```yaml
name: api
headers:
  X-App-Id: string
```

When you define global headers in your `api.yml`, you must [include them in your endpoint examples](/learn/api-definitions/ferndef/examples#examples-with-headers).

## Global path parameters

You can specify path parameters that are meant to be included on every request:

#### api.yml

```yaml
name: api
base-path: /{userId}/{orgId}
path-parameters:
  userId: string
  orgId: string
```

### Overriding the base path

If you have certain endpoints that don't live at the configured `base-path`, you can
override the `base-path` at the endpoint level.

**`imdb.yml`**

```yml imdb.yml {5}
service: 
  endpoints: 
    getMovie: 
      method: POST
      base-path: "override/{arg}"
      path: "movies/{movieId}"
      path-parameters: 
        arg: string
```

## Global query parameters

You can't yet specify query parameters that are meant to be included on every request.
If you'd like to see this feature, upvote [this issue](https://github.com/fern-api/fern/issues/2930).

## Idempotency headers

Configure idempotency headers to define which headers [SDK users](/learn/sdks/deep-dives/idempotency) can specify for safe request retries. You must also [mark each endpoint as idempotent](/learn/api-definitions/ferndef/endpoints/overview#idempotent-endpoints) for the headers to be exposed. When both are configured, Fern's generated SDKs expose these headers as parameters for idempotent endpoint calls.

**`api.yml`**

```yaml title="api.yml"
name: api
auth: bearer
idempotency-headers:
  Idempotency-Key: string
  Idempotency-Expiration: optional<integer>
```

Each key in `idempotency-headers` is the HTTP header name, and the value is the type. [SDK users](/learn/sdks/deep-dives/idempotency) can then specify these headers when calling idempotent endpoints.

> Specify global headers, path parameters or query parameters meant to be included on every request.