Functions_Extension_Version

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In this comprehensive article, I’ll walk you through everything you need to know about Functions_Extension_Version – from basic concepts to advanced implementation strategies.

Functions_Extension_Version

What is FUNCTIONS_EXTENSION_VERSION?

Functions_Extension_Version is an application setting that determines which version of the Azure Functions runtime your function app uses. This setting is crucial because it:

  • Controls which language features are available
  • Determines API compatibility
  • Affects performance characteristics
  • Influences the security posture

This setting lets you target specific runtime versions for each function app in your environment.

By using this settings, you can target a particular version for your Azure Function App. You can also use it to update the version of your Azure Function to a previous or current version.

Available Runtime Versions

Below are the major Azure Functions runtime versions

VersionStatusKey FeaturesSupport Status
~4CurrentEnhanced performance, expanded language supportFully supported
~3Legacy.NET Core 3.1 supportEnd of extended support
~2Legacy.NET Core 2.x supportEnd of extended support
~1Legacy.NET Framework supportEnd of extended support

How to Check Your Current Runtime Version

Before making changes, let’s verify which runtime version our function app is using

Approach-1 Using Azure Portal

  1. Navigate to your function app in the Azure portal
  2. Select “Configuration” from the left menu
  3. Look for the FUNCTIONS_EXTENSION_VERSION Setting under Application Settings as shown in the screenshot below.
functions_extension_version azure function

Approach-2 Using Azure CLI

We can execute the following Azure CLI command for the same purpose

az functionapp config appsettings list --name <FUNCTION_APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --query "[?name=='FUNCTIONS_EXTENSION_VERSION']"

Setting the Runtime Version

There are several methods to set or update your Azure FUNCTIONS_EXTENSION_VERSION. Let’s explore each approach

Approach 1: Using Azure Portal

  1. Log in to the Azure Portal (https://portal.azure.com/)
  2. Navigate to the Azure Function App, click on the configuration from the left navigation, and then click FUNCTIONS_EXTENSION_VERSION.
FUNCTIONS_EXTENSION_VERSION

3. Once you click on that, you can change the FUNCTIONS_EXTENSION_VERSION value and then click on the OK button as shown below

azure functions_extension_version

4. Next, click the Save button on the Application settings page to apply the changes.

Approach 2: Using PowerShell

We can also use the below Azure PowerShell command to update or change the Azure function functions_extension_version.

Update-AzFunctionAppSetting -Name <FUNCTION_APP_NAME> -ResourceGroupName <RESOURCE_GROUP_NAME> -AppSetting @{"FUNCTIONS_EXTENSION_VERSION" = "~4"}

Example

I am executing the Azure PowerShell command below to update the Azure Functions extension version to “~4”.

Update-AzFunctionAppSetting -Name azurelessons -ResourceGroupName myresgrp -AppSetting @{"FUNCTIONS_EXTENSION_VERSION" = "~4"}

After executing the above query, I got the expected output as per the screenshot below.

functions_extension_version 4

Approach 3: Using Azure CLI

We can also execute the Azure CLI command for the same purpose.

az functionapp config appsettings set --name <FUNCTION_APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --settings FUNCTIONS_EXTENSION_VERSION="~4"

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