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# AWS::EC2::EC2Fleet CapacityReservationOptionsRequest
<a name="aws-properties-ec2-ec2fleet-capacityreservationoptionsrequest"></a>

Describes the strategy for using unused Capacity Reservations for fulfilling On-Demand capacity.

**Note**  
This strategy can only be used if the EC2 Fleet is of type `instant`.

For more information about Capacity Reservations, see [On-Demand Capacity Reservations](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-capacity-reservations.html) in the *Amazon EC2 User Guide*. For examples of using Capacity Reservations in an EC2 Fleet, see [EC2 Fleet example configurations](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-fleet-examples.html) in the *Amazon EC2 User Guide*.

## Syntax
<a name="aws-properties-ec2-ec2fleet-capacityreservationoptionsrequest-syntax"></a>

To declare this entity in your CloudFormation template, use the following syntax:

### JSON
<a name="aws-properties-ec2-ec2fleet-capacityreservationoptionsrequest-syntax.json"></a>

```
{
  "[UsageStrategy](#cfn-ec2-ec2fleet-capacityreservationoptionsrequest-usagestrategy)" : String
}
```

### YAML
<a name="aws-properties-ec2-ec2fleet-capacityreservationoptionsrequest-syntax.yaml"></a>

```
  [UsageStrategy](#cfn-ec2-ec2fleet-capacityreservationoptionsrequest-usagestrategy): String
```

## Properties
<a name="aws-properties-ec2-ec2fleet-capacityreservationoptionsrequest-properties"></a>

`UsageStrategy`  <a name="cfn-ec2-ec2fleet-capacityreservationoptionsrequest-usagestrategy"></a>
Indicates whether to use unused Capacity Reservations for fulfilling On-Demand capacity.  
If you specify `use-capacity-reservations-first`, the fleet uses unused Capacity Reservations to fulfill On-Demand capacity up to the target On-Demand capacity. If multiple instance pools have unused Capacity Reservations, the On-Demand allocation strategy (`lowest-price` or `prioritized`) is applied. If the number of unused Capacity Reservations is less than the On-Demand target capacity, the remaining On-Demand target capacity is launched according to the On-Demand allocation strategy (`lowest-price` or `prioritized`).  
If you do not specify a value, the fleet fulfils the On-Demand capacity according to the chosen On-Demand allocation strategy.  
*Required*: No  
*Type*: String  
*Allowed values*: `use-capacity-reservations-first`  
*Update requires*: [Replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)