# Method request behavior for payloads without mapping templates for REST APIs in API Gateway
Method request behavior for payloads without mapping templates

If your method request has a payload and you don't have a mapping template defined for the `Content-Type` header, you can choose to pass the client-supplied request payload through the integration request to the backend without transformation. The process is known as integration passthrough. 

 The actual passthrough behavior of an incoming request is determined by this setting. There are three options: 

**When no template matches the request Content-Type header**  
Choose this option if you want the method request body to pass through the integration request to the backend without transformation when the method request content type does not match any content types associated with the mapping templates.  
When calling the API Gateway API, you choose this option by setting `WHEN_NO_MATCH` as the `passthroughBehavior` property value on the [Integration](https://docs.aws.amazon.com/apigateway/latest/api/API_Integration.html).

**When there are no templates defined (recommended)**  
Choose this option if you want the method request body to pass through the integration request to the backend without transformation when no mapping template is defined in the integration request. If a template is defined when this option is selected, the method request with a payload and content type that doesn't match any defined mapping template will be rejected with an HTTP 415 Unsupported Media Type response.  
When calling the API Gateway API, you choose this option by setting `WHEN_NO_TEMPLATES` as the `passthroughBehavior` property value on the [Integration](https://docs.aws.amazon.com/apigateway/latest/api/API_Integration.html).

**Never**  
Choose this option if you do not want the method request body to pass through the integration request to the backend without transformation when no mapping template is defined in the integration request. If a template is defined when this option is selected, the method request of an unmapped content type will be rejected with an HTTP 415 Unsupported Media Type response.   
When calling the API Gateway API, you choose this option by setting `NEVER` as the `passthroughBehavior` property value on the [Integration](https://docs.aws.amazon.com/apigateway/latest/api/API_Integration.html).

 The following examples show the possible passthrough behaviors. 

Example 1: One mapping template is defined in the integration request for the `application/json` content type.


| Content-type | Passthrough option | Behavior | 
| --- | --- | --- | 
| None API Gateway defaults to `application/json` | WHEN\$1NO\$1MATCH | The request payload is transformed using the template. | 
| None API Gateway defaults to `application/json` | WHEN\$1NO\$1TEMPLATES | The request payload is transformed using the template. | 
| None API Gateway defaults to `application/json` | NEVER | The request payload is transformed using the template. | 
| application/json | WHEN\$1NO\$1MATCH | The request payload is transformed using the template. | 
| application/json | WHEN\$1NO\$1TEMPLATES | The request payload is transformed using the template. | 
| application/json | NEVER | The request payload is transformed using the template. | 
| application/xml | WHEN\$1NO\$1MATCH | The request payload is not transformed and is sent to the backend as-is. | 
| application/xml | WHEN\$1NO\$1TEMPLATES | The request is rejected with an HTTP 415 Unsupported Media Type response. | 
| application/xml | NEVER | The request is rejected with an HTTP 415 Unsupported Media Type response. | 

Example 2: One mapping template is defined in the integration request for the `application/xml` content type.


| Content-type | Passthrough option | Behavior | 
| --- | --- | --- | 
| None API Gateway defaults to `application/json` | WHEN\$1NO\$1MATCH | The request payload is not transformed and is sent to the backend as-is. | 
| None API Gateway defaults to `application/json` | WHEN\$1NO\$1TEMPLATES | The request is rejected with an HTTP 415 Unsupported Media Type response. | 
| None API Gateway defaults to `application/json` | NEVER | The request is rejected with an HTTP 415 Unsupported Media Type response. | 
| application/json | WHEN\$1NO\$1MATCH | The request payload is not transformed and is sent to the backend as-is. | 
| application/json | WHEN\$1NO\$1TEMPLATES | The request is rejected with an HTTP 415 Unsupported Media Type response. | 
| application/json | NEVER | The request is rejected with an HTTP 415 Unsupported Media Type response. | 
| application/xml | WHEN\$1NO\$1MATCH | The request payload is transformed using the template. | 
| application/xml | WHEN\$1NO\$1TEMPLATES | The request payload is transformed using the template. | 
| application/xml | NEVER | The request payload is transformed using the template. | 

Example 3: No mapping templates are defined in the integration request.


| Content-type | Passthrough option | Behavior | 
| --- | --- | --- | 
| None API Gateway defaults to `application/json` | WHEN\$1NO\$1MATCH | The request payload is not transformed and is sent to the backend as-is. | 
| None API Gateway defaults to `application/json` | WHEN\$1NO\$1TEMPLATES | The request payload is not transformed and is sent to the backend as-is. | 
| None API Gateway defaults to `application/json` | NEVER | The request is rejected with an HTTP 415 Unsupported Media Type response. | 
| application/json | WHEN\$1NO\$1MATCH | The request payload is not transformed and is sent to the backend as-is. | 
| application/json | WHEN\$1NO\$1TEMPLATES | The request payload is not transformed and is sent to the backend as-is. | 
| application/json | NEVER | The request is rejected with an HTTP 415 Unsupported Media Type response. | 
| application/xml | WHEN\$1NO\$1MATCH | The request payload is not transformed and is sent to the backend as-is. | 
| application/xml | WHEN\$1NO\$1TEMPLATES | The request payload is not transformed and is sent to the backend as-is. | 
| application/xml | NEVER | The request is rejected with an HTTP 415 Unsupported Media Type response. |