App settings reference for Azure Functions

Application settings in a function app contain configuration options that affect all functions for that function app. These settings are accessed as environment variables. This article lists the app settings that are available in function apps.

There are several ways that you can add, update, and delete function app settings:

• In the Azure portal.
• By using the Azure CLI.
• By using Azure PowerShell.

Changes to function app settings require your function app to be restarted.

In this article, example connection string values are truncated for readability.

App setting considerations

When using app settings, you should be aware of the following considerations:

• Changes to function app settings require your function app to be restarted.

• In setting names, double-underscore (__) and semicolon (:) are considered reserved values. Double-underscores are interpreted as hierarchical delimiters on both Windows and Linux, and colons are interpreted in the same way only on Linux. For example, the setting AzureFunctionsWebHost__hostid=somehost_123456 would be interpreted as the following JSON object:

  "AzureFunctionsWebHost": {
      "hostid": "somehost_123456"
  }
  

  In this article, only double-underscores are used, since they're supported on both operating systems.

• When Functions runs locally, app settings are specified in the Values collection in the local.settings.json.

• There are other function app configuration options in the host.json file and in the local.settings.json file.

• You can use application settings to override host.json setting values without having to change the host.json file itself. This is helpful for scenarios where you need to configure or modify specific host.json settings for a specific environment. This also lets you change host.json settings without having to republish your project. To learn more, see the host.json reference article.

• This article documents the settings that are most relevant to your function apps. Because Azure Functions runs on App Service, other application settings may also be supported. For more information, see Environment variables and app settings in Azure App Service.

• Some scenarios also require you to work with settings documented in App Service site settings.

• Changing any read-only App Service application settings can put your function app into an unresponsive state.

• Take care when updating application settings by using REST APIs, including ARM templates. Because these APIs replace the existing application settings, you must include all existing settings when adding or modifying settings using REST APIs or ARM templates. When possible use Azure CLI or Azure PowerShell to programmatically work with application settings. For more information, see Work with application settings.

APPINSIGHTS_INSTRUMENTATIONKEY

The instrumentation key for Application Insights. Don't use both APPINSIGHTS_INSTRUMENTATIONKEY and APPLICATIONINSIGHTS_CONNECTION_STRING. When possible, use APPLICATIONINSIGHTS_CONNECTION_STRING. When Application Insights runs in a sovereign cloud, you must use APPLICATIONINSIGHTS_CONNECTION_STRING. For more information, see How to configure monitoring for Azure Functions.

Key	Sample value
APPINSIGHTS_INSTRUMENTATIONKEY	55555555-af77-484b-9032-64f83bb83bb

Don't use both APPINSIGHTS_INSTRUMENTATIONKEY and APPLICATIONINSIGHTS_CONNECTION_STRING. Use of APPLICATIONINSIGHTS_CONNECTION_STRING is recommended.

Note

On March 31, 2025, support for instrumentation key ingestion will end. Instrumentation key ingestion will continue to work, but we'll no longer provide updates or support for the feature. Transition to connection strings to take advantage of new capabilities.

APPLICATIONINSIGHTS_CONNECTION_STRING

The connection string for Application Insights. Don't use both APPINSIGHTS_INSTRUMENTATIONKEY and APPLICATIONINSIGHTS_CONNECTION_STRING. While the use of APPLICATIONINSIGHTS_CONNECTION_STRING is recommended in all cases, it's required in the following cases:

• When your function app requires the added customizations supported by using the connection string.
• When your Application Insights instance runs in a sovereign cloud, which requires a custom endpoint.

For more information, see Connection strings.

Key	Sample value
APPLICATIONINSIGHTS_CONNECTION_STRING	InstrumentationKey=...

AZURE_FUNCTION_PROXY_DISABLE_LOCAL_CALL

By default, Functions proxies use a shortcut to send API calls from proxies directly to functions in the same function app. This shortcut is used instead of creating a new HTTP request. This setting allows you to disable that shortcut behavior.

Key	Value	Description
AZURE_FUNCTION_PROXY_DISABLE_LOCAL_CALL	true	Calls with a backend URL pointing to a function in the local function app won't be sent directly to the function. Instead, the requests are directed back to the HTTP frontend for the function app.
AZURE_FUNCTION_PROXY_DISABLE_LOCAL_CALL	false	Calls with a backend URL pointing to a function in the local function app are forwarded directly to the function. false is the default value.

AZURE_FUNCTION_PROXY_BACKEND_URL_DECODE_SLASHES

This setting controls whether the characters %2F are decoded as slashes in route parameters when they're inserted into the backend URL.

Key	Value	Description
AZURE_FUNCTION_PROXY_BACKEND_URL_DECODE_SLASHES	true	Route parameters with encoded slashes are decoded.
AZURE_FUNCTION_PROXY_BACKEND_URL_DECODE_SLASHES	false	All route parameters are passed along unchanged, which is the default behavior.

For example, consider the proxies.json file for a function app at the myfunction.com domain.

{
    "$schema": "http://json.schemastore.org/proxies",
    "proxies": {
        "root": {
            "matchCondition": {
                "route": "/{*all}"
            },
            "backendUri": "example.com/{all}"
        }
    }
}

When AZURE_FUNCTION_PROXY_BACKEND_URL_DECODE_SLASHES is set to true, the URL example.com/api%2ftest resolves to example.com/api/test. By default, the URL remains unchanged as example.com/test%2fapi. For more information, see Functions proxies.

AZURE_FUNCTIONS_ENVIRONMENT

In version 2.x and later versions of the Functions runtime, configures app behavior based on the runtime environment. This value is read during initialization, and can be set to any value. Only the values of Development, Staging, and Production are honored by the runtime. When this application setting isn't present when running in Azure, the environment is assumed to be Production. Use this setting instead of ASPNETCORE_ENVIRONMENT if you need to change the runtime environment in Azure to something other than Production. The Azure Functions Core Tools set AZURE_FUNCTIONS_ENVIRONMENT to Development when running on a local computer, and this setting can't be overridden in the local.settings.json file. To learn more, see Environment-based Startup class and methods.

AzureFunctionsJobHost__*

In version 2.x and later versions of the Functions runtime, application settings can override host.json settings in the current environment. These overrides are expressed as application settings named AzureFunctionsJobHost__path__to__setting. For more information, see Override host.json values.

AzureFunctionsWebHost__hostid

Sets the host ID for a given function app, which should be a unique ID. This setting overrides the automatically generated host ID value for your app. Use this setting only when you need to prevent host ID collisions between function apps that share the same storage account.

A host ID must meet the following requirements:

• Be between 1 and 32 characters
• contain only lowercase letters, numbers, and dashes
• Not start or end with a dash
• Not contain consecutive dashes

An easy way to generate an ID is to take a GUID, remove the dashes, and make it lower case, such as by converting the GUID 1835D7B5-5C98-4790-815D-072CC94C6F71 to the value 1835d7b55c984790815d072cc94c6f71.

Key	Sample value
AzureFunctionsWebHost__hostid	myuniquefunctionappname123456789

For more information, see Host ID considerations.

AzureWebJobsDashboard

Optional storage account connection string for storing logs and displaying them in the Monitor tab in the portal. This setting is only valid for apps that target version 1.x of the Azure Functions runtime. The storage account must be a general-purpose one that supports blobs, queues, and tables. To learn more, see Storage account requirements.

Key	Sample value
AzureWebJobsDashboard	DefaultEndpointsProtocol=https;AccountName=...

Note

For better performance and experience, runtime version 2.x and later versions use APPINSIGHTS_INSTRUMENTATIONKEY and App Insights for monitoring instead of AzureWebJobsDashboard.

AzureWebJobsDisableHomepage

A value of true disables the default landing page that is shown for the root URL of a function app. The default value is false.

Key	Sample value
AzureWebJobsDisableHomepage	true

When this app setting is omitted or set to false, a page similar to the following example is displayed in response to the URL <functionappname>.azurewebsites.net.

AzureWebJobsDotNetReleaseCompilation

true means use Release mode when compiling .NET code; false means use Debug mode. Default is true.

Key	Sample value
AzureWebJobsDotNetReleaseCompilation	true

AzureWebJobsFeatureFlags

A comma-delimited list of beta features to enable. Beta features enabled by these flags aren't production ready, but can be enabled for experimental use before they go live.

Key	Sample value
AzureWebJobsFeatureFlags	feature1,feature2,EnableProxies

Add EnableProxies to this list to re-enable proxies on version 4.x of the Functions runtime while you plan your migration to Azure API Management. For more information, see Re-enable proxies in Functions v4.x.

AzureWebJobsKubernetesSecretName

Indicates the Kubernetes Secrets resource used for storing keys. Supported only when running in Kubernetes. This setting requires you to set AzureWebJobsSecretStorageType to kubernetes. When AzureWebJobsKubernetesSecretName isn't set, the repository is considered read-only. In this case, the values must be generated before deployment. The Azure Functions Core Tools generates the values automatically when deploying to Kubernetes.

Key	Sample value
AzureWebJobsKubernetesSecretName	<SECRETS_RESOURCE>

To learn more, see Secret repositories.

AzureWebJobsSecretStorageKeyVaultClientId

The client ID of the user-assigned managed identity or the app registration used to access the vault where keys are stored. This setting requires you to set AzureWebJobsSecretStorageType to keyvault. Supported in version 4.x and later versions of the Functions runtime.

Key	Sample value
AzureWebJobsSecretStorageKeyVaultClientId	<CLIENT_ID>

To learn more, see Secret repositories.

AzureWebJobsSecretStorageKeyVaultClientSecret

The secret for client ID of the user-assigned managed identity or the app registration used to access the vault where keys are stored. This setting requires you to set AzureWebJobsSecretStorageType to keyvault. Supported in version 4.x and later versions of the Functions runtime.

Key	Sample value
AzureWebJobsSecretStorageKeyVaultClientSecret	<CLIENT_SECRET>

To learn more, see Secret repositories.

AzureWebJobsSecretStorageKeyVaultName

The name of a key vault instance used to store keys. This setting is only supported for version 3.x of the Functions runtime. For version 4.x, instead use AzureWebJobsSecretStorageKeyVaultUri. This setting requires you to set AzureWebJobsSecretStorageType to keyvault.

The vault must have an access policy corresponding to the system-assigned managed identity of the hosting resource. The access policy should grant the identity the following secret permissions: Get,Set, List, and Delete.
When your functions run locally, the developer identity is used, and settings must be in the local.settings.json file.

Key	Sample value
AzureWebJobsSecretStorageKeyVaultName	<VAULT_NAME>

To learn more, see Secret repositories.

AzureWebJobsSecretStorageKeyVaultTenantId

The tenant ID of the app registration used to access the vault where keys are stored. This setting requires you to set AzureWebJobsSecretStorageType to keyvault. Supported in version 4.x and later versions of the Functions runtime. To learn more, see Secret repositories.

Key	Sample value
AzureWebJobsSecretStorageKeyVaultTenantId	<TENANT_ID>

AzureWebJobsSecretStorageKeyVaultUri

The URI of a key vault instance used to store keys. Supported in version 4.x and later versions of the Functions runtime. This is the recommended setting for using a key vault instance for key storage. This setting requires you to set AzureWebJobsSecretStorageType to keyvault.

The AzureWebJobsSecretStorageKeyVaultUri value should be the full value of Vault URI displayed in the Key Vault overview tab, including https://.

The vault must have an access policy corresponding to the system-assigned managed identity of the hosting resource. The access policy should grant the identity the following secret permissions: Get,Set, List, and Delete.
When your functions run locally, the developer identity is used, and settings must be in the local.settings.json file.

Key	Sample value
AzureWebJobsSecretStorageKeyVaultUri	https://<VAULT_NAME>.vault.azure.net

To learn more, see Use Key Vault references for Azure Functions.

AzureWebJobsSecretStorageSas

A Blob Storage SAS URL for a second storage account used for key storage. By default, Functions uses the account set in AzureWebJobsStorage. When using this secret storage option, make sure that AzureWebJobsSecretStorageType isn't explicitly set or is set to blob. To learn more, see Secret repositories.

Key	Sample value
AzureWebJobsSecretStorageSas	<BLOB_SAS_URL>

AzureWebJobsSecretStorageType

Specifies the repository or provider to use for key storage. Keys are always encrypted before being stored using a secret unique to your function app.

Key	Value	Description
AzureWebJobsSecretStorageType	blob	Keys are stored in a Blob storage container in the account provided by the AzureWebJobsStorage setting. Blob storage is the default behavior when AzureWebJobsSecretStorageType isn't set. To specify a different storage account, use the AzureWebJobsSecretStorageSas setting to indicate the SAS URL of a second storage account.
AzureWebJobsSecretStorageType	files	Keys are persisted on the file system. This is the default behavior for Functions v1.x.
AzureWebJobsSecretStorageType	keyvault	Keys are stored in a key vault instance set by AzureWebJobsSecretStorageKeyVaultName.
AzureWebJobsSecretStorageType	kubernetes	Supported only when running the Functions runtime in Kubernetes. When AzureWebJobsKubernetesSecretName isn't set, the repository is considered read-only. In this case, the values must be generated before deployment. The Azure Functions Core Tools generates the values automatically when deploying to Kubernetes.

To learn more, see Secret repositories.

AzureWebJobsStorage

The Azure Functions runtime uses this storage account connection string for normal operation. Some uses of this storage account include key management, timer trigger management, and Event Hubs checkpoints. The storage account must be a general-purpose one that supports blobs, queues, and tables. See Storage account and Storage account requirements.

Key	Sample value
AzureWebJobsStorage	DefaultEndpointsProtocol=https;AccountName=...

AzureWebJobs_TypeScriptPath

Path to the compiler used for TypeScript. Allows you to override the default if you need to.

Key	Sample value
AzureWebJobs_TypeScriptPath	%HOME%\typescript

DOCKER_SHM_SIZE

Sets the shared memory size (in bytes) when the Python worker is using shared memory. To learn more, see Shared memory.

Key	Sample value
DOCKER_SHM_SIZE	268435456

The value above sets a shared memory size of ~256 MB.

Requires that FUNCTIONS_WORKER_SHARED_MEMORY_DATA_TRANSFER_ENABLED be set to 1.

ENABLE_ORYX_BUILD

Indicates whether the Oryx build system is used during deployment. ENABLE_ORYX_BUILD must be set to true when doing remote build deployments to Linux. For more information, see Remote build on Linux.

Key	Sample value
ENABLE_ORYX_BUILD	true

FUNCTION_APP_EDIT_MODE

Dictates whether editing in the Azure portal is enabled. Valid values are readwrite and readonly.

Key	Sample value
FUNCTION_APP_EDIT_MODE	readonly

FUNCTIONS_EXTENSION_VERSION

The version of the Functions runtime that hosts your function app. A tilde (~) with major version means use the latest version of that major version (for example, ~3). When new versions for the same major version are available, they're automatically installed in the function app. To pin the app to a specific version, use the full version number (for example, 3.0.12345). Default is ~3. A value of ~1 pins your app to version 1.x of the runtime. For more information, see Azure Functions runtime versions overview. A value of ~4 means that your app runs on version 4.x of the runtime, which supports .NET 6.0.

Key	Sample value
FUNCTIONS_EXTENSION_VERSION	~4

The following major runtime version values are supported:

Value	Runtime target	Comment
~4	4.x	Recommended
~3	3.x	Support ends December 13, 2022
~2	2.x	No longer supported
~1	1.x	Supported

FUNCTIONS_V2_COMPATIBILITY_MODE

This setting enables your function app to run in a version 2.x compatible mode on the version 3.x runtime. Use this setting only if encountering issues after upgrading your function app from version 2.x to 3.x of the runtime.

Important

This setting is intended only as a short-term workaround while you update your app to run correctly on version 3.x. This setting is supported as long as the 2.x runtime is supported. If you encounter issues that prevent your app from running on version 3.x without using this setting, please report your issue.

You must also set FUNCTIONS_EXTENSION_VERSION to ~3.

Key	Sample value
FUNCTIONS_V2_COMPATIBILITY_MODE	true

FUNCTIONS_REQUEST_BODY_SIZE_LIMIT

Overrides the default limit on the body size of requests sent to HTTP endpoints. The value is given in bytes, with a default maximum request size of 104857600 bytes.

Key	Sample value
FUNCTIONS_REQUEST_BODY_SIZE_LIMIT	250000000

FUNCTIONS_WORKER_PROCESS_COUNT

Specifies the maximum number of language worker processes, with a default value of 1. The maximum value allowed is 10. Function invocations are evenly distributed among language worker processes. Language worker processes are spawned every 10 seconds until the count set by FUNCTIONS_WORKER_PROCESS_COUNT is reached. Using multiple language worker processes isn't the same as scaling. Consider using this setting when your workload has a mix of CPU-bound and I/O-bound invocations. This setting applies to all language runtimes, except for .NET running in process (dotnet).

Key	Sample value
FUNCTIONS_WORKER_PROCESS_COUNT	2

FUNCTIONS_WORKER_RUNTIME

The language worker runtime to load in the function app. This corresponds to the language being used in your application (for example, dotnet). Starting with version 2.x of the Azure Functions runtime, a given function app can only support a single language.

Key	Sample value
FUNCTIONS_WORKER_RUNTIME	node

Valid values:

Value	Language
dotnet	C# (class library) C# (script)
dotnet-isolated	C# (isolated worker process)
java	Java
node	JavaScript TypeScript
powershell	PowerShell
python	Python
custom	Other

FUNCTIONS_WORKER_SHARED_MEMORY_DATA_TRANSFER_ENABLED

This setting enables the Python worker to use shared memory to improve throughput. Enable shared memory when your Python function app is hitting memory bottlenecks.

Key	Sample value
FUNCTIONS_WORKER_SHARED_MEMORY_DATA_TRANSFER_ENABLED	1

With this setting enabled, you can use the DOCKER_SHM_SIZE setting to set the shared memory size. To learn more, see Shared memory.

JAVA_OPTS

Used to customize the Java virtual machine (JVM) used to run your Java functions when running on a Premium plan or Dedicated plan. When running on a Consumption plan, instead use languageWorkers__java__arguments. For more information, see Customize JVM.

languageWorkers__java__arguments

Used to customize the Java virtual machine (JVM) used to run your Java functions when running on a Consumption plan. This setting does increase the cold start times for Java functions running in a Consumption plan. For a Premium or Dedicated plan, instead use JAVA_OPTS. For more information, see Customize JVM.

MDMaxBackgroundUpgradePeriod

Controls the managed dependencies background update period for PowerShell function apps, with a default value of 7.00:00:00 (weekly).

Each PowerShell worker process initiates checking for module upgrades on the PowerShell Gallery on process start and every MDMaxBackgroundUpgradePeriod after that. When a new module version is available in the PowerShell Gallery, it's installed to the file system and made available to PowerShell workers. Decreasing this value lets your function app get newer module versions sooner, but it also increases the app resource usage (network I/O, CPU, storage). Increasing this value decreases the app's resource usage, but it may also delay delivering new module versions to your app.

Key	Sample value
MDMaxBackgroundUpgradePeriod	7.00:00:00

To learn more, see Dependency management.

MDNewSnapshotCheckPeriod

Specifies how often each PowerShell worker checks whether managed dependency upgrades have been installed. The default frequency is 01:00:00 (hourly).

After new module versions are installed to the file system, every PowerShell worker process must be restarted. Restarting PowerShell workers affects your app availability as it can interrupt current function execution. Until all PowerShell worker processes are restarted, function invocations may use either the old or the new module versions. Restarting all PowerShell workers completes within MDNewSnapshotCheckPeriod.

Within every MDNewSnapshotCheckPeriod, the PowerShell worker checks whether or not managed dependency upgrades have been installed. When upgrades have been installed, a restart is initiated. Increasing this value decreases the frequency of interruptions because of restarts. However, the increase might also increase the time during which function invocations could use either the old or the new module versions, non-deterministically.

Key	Sample value
MDNewSnapshotCheckPeriod	01:00:00

To learn more, see Dependency management.

MDMinBackgroundUpgradePeriod

The period of time after a previous managed dependency upgrade check before another upgrade check is started, with a default of 1.00:00:00 (daily).

To avoid excessive module upgrades on frequent Worker restarts, checking for module upgrades isn't performed when any worker has already initiated that check in the last MDMinBackgroundUpgradePeriod.

Key	Sample value
MDMinBackgroundUpgradePeriod	1.00:00:00

To learn more, see Dependency management.

PIP_INDEX_URL

This setting lets you override the base URL of the Python Package Index, which by default is https://pypi.org/simple. Use this setting when you need to run a remote build using custom dependencies. These custom dependencies can be in a package index repository compliant with PEP 503 (the simple repository API) or in a local directory that follows the same format.

Key	Sample value
PIP_INDEX_URL	http://my.custom.package.repo/simple

To learn more, see pip documentation for --index-url and using Custom dependencies in the Python developer reference.

PIP_EXTRA_INDEX_URL

The value for this setting indicates an extra index URL for custom packages for Python apps, to use in addition to the --index-url. Use this setting when you need to run a remote build using custom dependencies that are found in an extra package index. Should follow the same rules as --index-url.

Key	Sample value
PIP_EXTRA_INDEX_URL	http://my.custom.package.repo/simple

To learn more, see pip documentation for --extra-index-url and Custom dependencies in the Python developer reference.

PYTHON_ISOLATE_WORKER_DEPENDENCIES

The configuration is specific to Python function apps. It defines the prioritization of module loading order. By default, this value is set to 0.

Key	Value	Description
PYTHON_ISOLATE_WORKER_DEPENDENCIES	0	Prioritize loading the Python libraries from internal Python worker's dependencies, which is the default behavior. Third-party libraries defined in requirements.txt may be shadowed.
PYTHON_ISOLATE_WORKER_DEPENDENCIES	1	Prioritize loading the Python libraries from application's package defined in requirements.txt. This prevents your libraries from colliding with internal Python worker's libraries.

PYTHON_ENABLE_DEBUG_LOGGING

Enables debug-level logging in a Python function app. A value of 1 enables debug-level logging. Without this setting or with a value of 0, only information and higher level logs are sent from the Python worker to the Functions host. Use this setting when debugging or tracing your Python function executions.

When debugging Python functions, make sure to also set a debug or trace logging level in the host.json file, as needed. To learn more, see How to configure monitoring for Azure Functions.

PYTHON_ENABLE_WORKER_EXTENSIONS

The configuration is specific to Python function apps. Setting this to 1 allows the worker to load in Python worker extensions defined in requirements.txt. It enables your function app to access new features provided by third-party packages. It may also change the behavior of function load and invocation in your app. Ensure the extension you choose is trustworthy as you bear the risk of using it. Azure Functions gives no express warranties to any extensions. For how to use an extension, visit the extension's manual page or readme doc. By default, this value sets to 0.

Key	Value	Description
PYTHON_ENABLE_WORKER_EXTENSIONS	0	Disable any Python worker extension.
PYTHON_ENABLE_WORKER_EXTENSIONS	1	Allow Python worker to load extensions from requirements.txt.

PYTHON_THREADPOOL_THREAD_COUNT

Specifies the maximum number of threads that a Python language worker would use to execute function invocations, with a default value of 1 for Python version 3.8 and below. For Python version 3.9 and above, the value is set to None. This setting doesn't guarantee the number of threads that would be set during executions. The setting allows Python to expand the number of threads to the specified value. The setting only applies to Python functions apps. Additionally, the setting applies to synchronous functions invocation and not for coroutines.

Key	Sample value	Max value
PYTHON_THREADPOOL_THREAD_COUNT	2	32

SCALE_CONTROLLER_LOGGING_ENABLED

This setting is currently in preview.

This setting controls logging from the Azure Functions scale controller. For more information, see Scale controller logs.

Key	Sample value
SCALE_CONTROLLER_LOGGING_ENABLED	AppInsights:Verbose

The value for this key is supplied in the format <DESTINATION>:<VERBOSITY>, which is defined as follows:

Property	Description
<DESTINATION>	The destination to which logs are sent. Valid values are AppInsights and Blob. When you use AppInsights, ensure that the Application Insights is enabled in your function app. When you set the destination to Blob, logs are created in a blob container named azure-functions-scale-controller in the default storage account set in the AzureWebJobsStorage application setting.
<VERBOSITY>	Specifies the level of logging. Supported values are None, Warning, and Verbose. When set to Verbose, the scale controller logs a reason for every change in the worker count, and information about the triggers that factor into those decisions. Verbose logs include trigger warnings and the hashes used by the triggers before and after the scale controller runs.

Tip

Keep in mind that while you leave scale controller logging enabled, it impacts the potential costs of monitoring your function app. Consider enabling logging until you have collected enough data to understand how the scale controller is behaving, and then disabling it.

SCM_DO_BUILD_DURING_DEPLOYMENT

Controls remote build behavior during deployment. When SCM_DO_BUILD_DURING_DEPLOYMENT is set to true, the project is built remotely during deployment.

Key	Sample value
SCM_DO_BUILD_DURING_DEPLOYMENT	true

SCM_LOGSTREAM_TIMEOUT

Controls the timeout, in seconds, when connected to streaming logs. The default value is 7200 (2 hours).

Key	Sample value
SCM_LOGSTREAM_TIMEOUT	1800

The above sample value of 1800 sets a timeout of 30 minutes. To learn more, see Enable streaming logs.

WEBSITE_CONTENTAZUREFILECONNECTIONSTRING

Connection string for storage account where the function app code and configuration are stored in event-driven scaling plans. For more information, see Create a function app.

Key	Sample value
WEBSITE_CONTENTAZUREFILECONNECTIONSTRING	DefaultEndpointsProtocol=https;AccountName=...

This setting is required for Consumption plan apps on Windows and for Premium plan apps on both Windows and Linux. It's not required for Dedicated plan apps, which aren't dynamically scaled by Functions.

Changing or removing this setting may cause your function app to not start. To learn more, see this troubleshooting article.

WEBSITE_CONTENTOVERVNET

A value of 1 enables your function app to scale when you have your storage account restricted to a virtual network. You should enable this setting when restricting your storage account to a virtual network. To learn more, see Restrict your storage account to a virtual network.

Key	Sample value
WEBSITE_CONTENTOVERVNET	1

Supported on Premium and Dedicated (App Service) plans (Standard and higher). Not supported when running on a Consumption plan.

WEBSITE_CONTENTSHARE

The file path to the function app code and configuration in an event-driven scaling plans. Used with WEBSITE_CONTENTAZUREFILECONNECTIONSTRING. Default is a unique string generated by the runtime that begins with the function app name. See Create a function app.

Key	Sample value
WEBSITE_CONTENTSHARE	functionapp091999e2

This setting is required for Consumption and Premium plan apps on both Windows and Linux. It's not required for Dedicated plan apps, which aren't dynamically scaled by Functions.

Changing or removing this setting may cause your function app to not start. To learn more, see this troubleshooting article.

The following considerations apply when using an Azure Resource Manager (ARM) template to create a function app during deployment:

• When you don't set a WEBSITE_CONTENTSHARE value for the main function app or any apps in slots, unique share values are generated for you. Not setting WEBSITE_CONTENTSHARE is the recommended approach for an ARM template deployment.
• There are scenarios where you must set the WEBSITE_CONTENTSHARE value to a predefined share, such as when you use a secured storage account in a virtual network. In this case, you must set a unique share name for the main function app and the app for each deployment slot.
• Don't make WEBSITE_CONTENTSHARE a slot setting.
• When you specify WEBSITE_CONTENTSHARE, the value must follow this guidance for share names.

To learn more, see Automate resource deployment for your function app.

WEBSITE_DNS_SERVER

Sets the DNS server used by an app when resolving IP addresses. This setting is often required when using certain networking functionality, such as Azure DNS private zones and private endpoints.

Key	Sample value
WEBSITE_DNS_SERVER	168.63.129.16

WEBSITE_ENABLE_BROTLI_ENCODING

Controls whether Brotli encoding is used for compression instead of the default gzip compression. When WEBSITE_ENABLE_BROTLI_ENCODING is set to 1, Brotli encoding is used; otherwise gzip encoding is used.

WEBSITE_FUNCTIONS_ARMCACHE_ENABLED

Disables caching when deploying function apps using Azure Resource Manager (ARM) templates.

Key	Sample value
WEBSITE_FUNCTIONS_ARMCACHE_ENABLED	0

WEBSITE_MAX_DYNAMIC_APPLICATION_SCALE_OUT

The maximum number of instances that the app can scale out to. Default is no limit.

Important

This setting is in preview. An app property for function max scale out has been added and is the recommended way to limit scale out.

Key	Sample value
WEBSITE_MAX_DYNAMIC_APPLICATION_SCALE_OUT	5

WEBSITE_NODE_DEFAULT_VERSION

Windows only. Sets the version of Node.js to use when running your function app on Windows. You should use a tilde (~) to have the runtime use the latest available version of the targeted major version. For example, when set to ~18, the latest version of Node.js 18 is used. When a major version is targeted with a tilde, you don't have to manually update the minor version.

Key	Sample value
WEBSITE_NODE_DEFAULT_VERSION	~18

WEBSITE_OVERRIDE_STICKY_DIAGNOSTICS_SETTINGS

When performing a slot swap on Premium Functions it can fail to swap if the storage account associated with the Function App is network restricted. This is due to a legacy application logging feature that Functions and App Service share. This setting overrides that legacy logging feature and allows the swap to occur. Set to 0 in the production slot and mark it as a Deployment Slot setting (also known as sticky), or add to all slots to make sure that all version settings are also swapped.

Key	Sample value
WEBSITE_OVERRIDE_STICKY_DIAGNOSTICS_SETTINGS	0

WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS

By default, the version settings for function apps are specific to each slot. This setting is used when upgrading functions by using deployment slots. This prevents unanticipated behavior due to changing versions after a swap. Set to 0 in production and in the slot to make sure that all version settings are also swapped. For more information, see Upgrade using slots.

Key	Sample value
WEBSITE_OVERRIDE_STICKY_EXTENSION_VERSIONS	0

WEBSITE_RUN_FROM_PACKAGE

Enables your function app to run from a mounted package file.

Key	Sample value
WEBSITE_RUN_FROM_PACKAGE	1

Valid values are either a URL that resolves to the location of a deployment package file, or 1. When set to 1, the package must be in the d:\home\data\SitePackages folder. When you use zip deployment with WEBSITE_RUN_FROM_PACKAGE enabled, the package is automatically uploaded to this location. In preview, this setting was named WEBSITE_RUN_FROM_ZIP. For more information, see Run your functions from a package file.

WEBSITE_SKIP_CONTENTSHARE_VALIDATION

The WEBSITE_CONTENTAZUREFILECONNECTIONSTRING and WEBSITE_CONTENTSHARE settings have extra validation checks to ensure that the app can be properly started. Creation of application settings will fail if the function app can't properly call out to the downstream Storage Account or Key Vault due to networking constraints or other limiting factors. When WEBSITE_SKIP_CONTENTSHARE_VALIDATION is set to 1, the validation check is skipped; otherwise the value defaults to 0 and the validation will take place.

Key	Sample value
WEBSITE_SKIP_CONTENTSHARE_VALIDATION	1

If validation is skipped and either the connection string or content share isn't valid, the app won't be able to start properly. In this case, functions return HTTP 500 errors. For more information, see Troubleshoot error: "Azure Functions Runtime is unreachable"

WEBSITE_SLOT_NAME

Read-only. Name of the current deployment slot. The name of the production slot is Production.

Key	Sample value
WEBSITE_SLOT_NAME	Production

WEBSITE_TIME_ZONE

Allows you to set the timezone for your function app.

Key	OS	Sample value
WEBSITE_TIME_ZONE	Windows	Eastern Standard Time
WEBSITE_TIME_ZONE	Linux	America/New_York

The default time zone used with the CRON expressions is Coordinated Universal Time (UTC). To have your CRON expression based on another time zone, create an app setting for your function app named WEBSITE_TIME_ZONE.

The value of this setting depends on the operating system and plan on which your function app runs.

Operating system	Plan	Value
Windows	All	Set the value to the name of the desired time zone as given by the second line from each pair given by the Windows command tzutil.exe /L
Linux	Premium Dedicated	Set the value to the name of the desired time zone as shown in the tz database.

Note

WEBSITE_TIME_ZONE is not currently supported on the Linux Consumption plan.

For example, Eastern Time in the US (represented by Eastern Standard Time (Windows) or America/New_York (Linux)) currently uses UTC-05:00 during standard time and UTC-04:00 during daylight time. To have a timer trigger fire at 10:00 AM Eastern Time every day, create an app setting for your function app named WEBSITE_TIME_ZONE, set the value to Eastern Standard Time (Windows) or America/New_York (Linux), and then use the following NCRONTAB expression:

"0 0 10 * * *"

When you use WEBSITE_TIME_ZONE the time is adjusted for time changes in the specific timezone, including daylight saving time and changes in standard time.

WEBSITE_USE_PLACEHOLDER

Indicates whether to use a specific cold start optimization when running on the Consumption plan. Set to 0 to disable the cold-start optimization on the Consumption plan.

Key	Sample value
WEBSITE_USE_PLACEHOLDER	1

WEBSITE_VNET_ROUTE_ALL

Important

WEBSITE_VNET_ROUTE_ALL is a legacy app setting that has been replaced by the vnetRouteAllEnabled site setting.

Indicates whether all outbound traffic from the app is routed through the virtual network. A setting value of 1 indicates that all traffic is routed through the virtual network. You need this setting when using features of Regional virtual network integration. It's also used when a virtual network NAT gateway is used to define a static outbound IP address.

Key	Sample value
WEBSITE_VNET_ROUTE_ALL	1

App Service site settings

Some configurations must be maintained at the App Service level as site settings, such as language versions. These settings are managed in the portal, by using REST APIs, or by using Azure CLI or Azure PowerShell. The following are site settings that could be required, depending on your runtime language, OS, and versions:

linuxFxVersion

For function apps running on Linux, linuxFxVersion indicates the language and version for the language-specific worker process. This information is used, along with FUNCTIONS_EXTENSION_VERSION, to determine which specific Linux container image is installed to run your function app. This setting can be set to a pre-defined value or a custom image URI.

This value is set for you when you create your Linux function app. You may need to set it for ARM template and Bicep deployments and in certain upgrade scenarios.

Valid linuxFxVersion values

You can use the following Azure CLI command to see a table of current linuxFxVersion values, by supported Functions runtime version:

az functionapp list-runtimes --os linux --query "[].{stack:join(' ', [runtime, version]), LinuxFxVersion:linux_fx_version, SupportedFunctionsVersions:to_string(supported_functions_versions[])}" --output table

The previous command requires you to upgrade to version 2.40 of the Azure CLI.

Custom images

When you create and maintain your own custom linux container for your function app, the linuxFxVersion value is also in the format DOCKER|<IMAGE_URI>, as in the following example:

linuxFxVersion = "DOCKER|contoso.com/azurefunctionsimage:v1.0.0"

For more information, see Create a function on Linux using a custom container.

Important

When creating your own containers, you are required to keep the base image of your container updated to the latest supported base image. Supported base images for Azure Functions are language-specific and are found in the Azure Functions base image repos.

The Functions team is committed to publishing monthly updates for these base images. Regular updates include the latest minor version updates and security fixes for both the Functions runtime and languages. For containers, you should regularly update the base image in the Dockerfile, rebuild, and redeploy updated versions of your containers.

netFrameworkVersion

Sets the specific version of .NET for C# functions. For more information, see Upgrade your function app in Azure.

powerShellVersion

Sets the specific version of PowerShell on which your functions run. For more information, see Changing the PowerShell version.

When running locally, you instead use the FUNCTIONS_WORKER_RUNTIME_VERSION setting in the local.settings.json file.

vnetrouteallenabled

Indicates whether all outbound traffic from the app is routed through the virtual network. A setting value of 1 indicates that all traffic is routed through the virtual network. You need this setting when using features of Regional virtual network integration. It's also used when a virtual network NAT gateway is used to define a static outbound IP address. For more information, see Configure application routing.

This site setting replaces the legacy WEBSITE_VNET_ROUTE_ALL setting.

Next steps

Learn how to update app settings

See configuration settings in the host.json file

See other app settings for App Service apps