Frequently asked questions about scaling web apps in Azure App Service

This article answers common questions about scaling web apps in Azure App Service.

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How do I scale up a Web App?

You can scale up a Web App by using the Azure portal. On your Web App page, select Scale Up (App Service Plan) from the left menu. For more information, see Scale up an app in Azure App Service.

Is there any further action I need to perform before scaling up a Free App Service Plan?

Before you switch an App Service Plan from the Free tier, you must remove the spending limits in place for your Azure subscription. To view or change options for your Microsoft Azure App Service subscription, see Microsoft Azure Subscriptions - Remove spending limits.

Is there any instance limitation when scaling a Web App?

Yes, the limitation depends on the tier of the App Service Plan. For more information, see App Service limits.

Can I scale a Standard App Service Plan for more than 10 instances?

The Standard App Service Plan tier doesn't support more than 10 instances. You can move to a Premium App Service Plan and get the benefit of having 30 instances (in selected regions) per App Service Plan. To check the instance limit per pricing tier, see App Service limits.

Can I configure App Services on the same App Service Plan with a different number of instances?

You can configure it by enabling Per-App Scaling, and changing App Service's numberOfWorkers property to the desired instance count. For more information, see Per-App Scaling.

Why does scale up for my Web App also trigger scale up for another Web App?

Scaling happens on the entire App Service Plan. If you host multiple App Services in the same App Service Plan, all App Services in this App Service Plan will be scaled up.

Why isn't autoscale working as expected?

You might be running into a scenario in which we intentionally choose not to scale to avoid an infinite loop due to "flapping." This behavior usually happens when there isn't an adequate margin between the scale-out and scale-in thresholds. For more information about how to avoid "flapping" and other autoscale best practices, see Autoscale best practices.

How do I determine when an autoscale rule triggered scaling?

You can retrieve scale history from the activity log. Whenever your resource is scaled up or down, an event is logged in the activity log. You can view the scale history of your resource for the past 24 hours by switching to the Run history tab. To view the complete scale history (for up to 90 days), select Click here to see more details. For more information, see View the scale history of your resource.

Why does autoscale sometimes scale only partially?

Autoscale is triggered when metrics exceed preconfigured boundaries. Sometimes, you might notice that the capacity is only partially filled compared to what you expected. This behavior might occur when the number of instances you want isn't available. In that scenario, autoscale partially fills in with the available number of instances. Autoscale then runs the rebalance logic to get more capacity. It allocates the remaining instances, and this allocation might take a few minutes. If you don't see the expected number of instances after a few minutes, it might be because the partial refill was enough to bring the metrics within the boundaries. Or, autoscale might have scaled down because it reached the lower metrics boundary.

When I scale up an App Service Plan to a Premium V3 tier, the "Premium V3 is not supported for this scale unit. Please consider redeploying or cloning your app." error occurs. What should I do?

The Premium V3 feature requires the site to run on the newest hardware infrastructure. To scale up an App Service Plan to Premium V3, the Web App must be running in an App Service deployment that supports PremiumV3. For more information, see Scale up from an unsupported resource group and region combination.

I'm unable to scale up/scale down the App Service Plan due to the "You have exceeded the maximum amount of scale changes within the past hour (XX changes and limit is XX)" error. What should I do?

To avoid this issue, don't perform scaling operations that release more than XX instances in an hour. Every time you release an instance during a scale-down operation, the instance is rebooted to ensure the next App Service Plan can get a clean instance. When you perform too many scaling operations in quick succession, instance reboots can cause performance issues for other App Services. Therefore we intentionally put a throttling mechanism for scaling that prevents you from executing scaling operations more than the acceptable limit in quick succession.

My Web App is using the Diagnostic setting "AppServiceFileAuditLogs" and I'm unable to scale the App Service Plan from Premium V2 to the Basic tier. What should I do?

The file change audit logs "AppServiceFileAuditLogs" are only available for App Services in Premium, PremiumV2, and Isolated App Service Plans. If you need "AppServiceFileAuditLogs," you won't be able to scale down to the Basic tier. To have these audit logs available, configure your App Service Plan for Premium or higher tier.

Contact us for help

If you have questions or need help, create a support request, or ask Azure community support. You can also submit product feedback to Azure feedback community.