Virtual Machine Scale Sets - Scale Out

Service:

Compute

API Version:

2026-03-01

Scales out one or more virtual machines in a VM scale set.

POST https://management.azure.com/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.Compute/virtualMachineScaleSets/{vmScaleSetName}/scaleOut?api-version=2026-03-01

URI Parameters

Name	In	Required	Type	Description
resourceGroupName	path	True	string minLength: 1 maxLength: 90	The name of the resource group. The name is case insensitive.
subscriptionId	path	True	string minLength: 1	The ID of the target subscription.
vmScaleSetName	path	True	string	The name of the VM scale set.
api-version	query	True	string minLength: 1	The API version to use for this operation.

Request Body

Name	Required	Type	Description
capacity	True	integer (int64)	Specifies the number of virtual machines in the scale set.
properties		VMScaleSetScaleOutInputProperties	The input properties for ScaleOut

Responses

Name	Type	Description
200 OK		The request has succeeded.
202 Accepted		Resource operation accepted. Headers Location: string Retry-After: integer
Other Status Codes	CloudError	An unexpected error response.

Security

azure_auth

Azure Active Directory OAuth2 Flow.

Type: oauth2
Flow: implicit
Authorization URL: https://login.microsoftonline.com/common/oauth2/authorize

Scopes

Name	Description
user_impersonation	impersonate your user account

Examples

VirtualMachineScaleSet Scale Out.

Sample request

HTTP

POST https://management.azure.com/subscriptions/{subscription-id}/resourceGroups/myResourceGroup/providers/Microsoft.Compute/virtualMachineScaleSets/{vmss-name}/scaleOut?api-version=2026-03-01

{
  "capacity": 5,
  "properties": {
    "zone": "1"
  }
}

Sample response

Status code:

200

Status code:

202

location: https://foo.com/operationstatus

Definitions

Name	Description
ApiError	Api error.
ApiErrorBase	Api error base.
CloudError	An error response from the Compute service.
InnerError	Inner error details.
VMScaleSetScaleOutInput	The input for ScaleOut
VMScaleSetScaleOutInputProperties	The input properties for ScaleOut

ApiError

Object

Api error.

Name	Type	Description
code	string	The error code.
details	ApiErrorBase[]	The Api error details
innererror	InnerError	The Api inner error
message	string	The error message.
target	string	The target of the particular error.

ApiErrorBase

Object

Api error base.

Name	Type	Description
code	string	The error code.
message	string	The error message.
target	string	The target of the particular error.

CloudError

Object

An error response from the Compute service.

Name	Type	Description
error	ApiError	Api error.

InnerError

Object

Inner error details.

Name	Type	Description
errordetail	string	The internal error message or exception dump.
exceptiontype	string	The exception type.

VMScaleSetScaleOutInput

Object

The input for ScaleOut

Name	Type	Description
capacity	integer (int64)	Specifies the number of virtual machines in the scale set.
properties	VMScaleSetScaleOutInputProperties	The input properties for ScaleOut

VMScaleSetScaleOutInputProperties

Object

The input properties for ScaleOut

Name	Type	Description
zone	string	The zone in which the scale out is requested for the virtual machine scale set.