Azure Functions Versions

Azure Functions supports multiple versions, allowing you to choose the runtime environment that best suits your needs and compatibility requirements. Each version offers different features, language support, and performance characteristics.

Important: It is highly recommended to use the latest stable version of Azure Functions for security updates, performance improvements, and access to new features. Always check the official Azure Functions documentation for the most up-to-date information on supported versions and their lifecycle.

Understanding Function Runtime Versions

The Azure Functions runtime version determines the underlying infrastructure and set of features available to your functions. Key aspects include:

Language Support: Different versions may have varying levels of support for different programming languages (e.g., .NET, Node.js, Python, Java, PowerShell).
Features: Newer versions often introduce new trigger and binding types, improved performance, and enhanced configuration options.
Compatibility: Ensure your function code and dependencies are compatible with the chosen runtime version.

Current Supported Versions

As of the latest update, the following Azure Functions runtime versions are generally supported. Please refer to the official Microsoft documentation for the most precise and current details.

Runtime Version	Release Date	Key Features / Notes	End-of-Life Date (Approximate)
`4.x`	October 2021	Latest major version. Supports latest language SDKs, improved performance, enhanced security features. Recommended for new projects.	Extended Support
`3.x`	October 2019	Stable release, widely used. Continues to receive updates.	December 2024
`2.x`	September 2018	Older version. Migration to 3.x or 4.x is recommended.	December 2022 (Extended Support Ended)
`1.x`	November 2016	Original version for Azure Functions. Only available for Consumption plan. Not recommended for new development.	September 2024 (Extended Support Ended)

How to Select a Runtime Version

You can specify the runtime version for your Azure Functions app in several ways:

1. Azure Portal

When creating a new Function App in the Azure portal, you can select the desired "Runtime stack" which includes the version. For existing apps, you can often change this setting under the "Configuration" blade.

2. Azure CLI

You can set the runtime version using the Azure CLI during app creation or update:

az functionapp create --resource-group MyResourceGroup --name MyFunctionApp --consumption-plan-location westus --runtime node --runtime-version 18 --functions-version 4
az functionapp update --resource-group MyResourceGroup --name MyFunctionApp --functions-version 4

3. Azure Resource Manager (ARM) Templates / Bicep

When defining your Function App in infrastructure-as-code, use the FUNCTIONS_EXTENSION_VERSION application setting:

{
  "type": "Microsoft.Web/sites",
  "apiVersion": "2021-02-01",
  "name": "[parameters('functionAppName')]",
  "properties": {
    "siteConfig": {
      "appSettings": [
        {
          "name": "FUNCTIONS_EXTENSION_VERSION",
          "value": "~4"
        }
        // ... other settings
      ]
    }
  }
}

Common values for FUNCTIONS_EXTENSION_VERSION include ~4, ~3, ~2, and ~1.

4. Host.json file

While not for the primary runtime version itself, the host.json file can configure specific aspects of the runtime for certain features. The runtime version is typically set globally for the Function App.

Tip: For local development using the Azure Functions Core Tools, you can also specify the runtime version. Ensure your local environment matches the version deployed to Azure to avoid unexpected behavior.

Deprecations and End-of-Life

Azure Functions runtime versions eventually reach their end-of-life and are no longer supported or updated. It's crucial to stay informed about these dates to plan your migration strategy. Running on unsupported versions can expose your applications to security vulnerabilities and prevent you from utilizing the latest Azure platform features.

Always refer to the official Azure Functions versioning documentation for the definitive lifecycle dates and guidance on migrating between versions.