Work with Azure Functions Core Tools

Azure Functions Core Tools lets you develop and test your functions on your local computer from the command prompt or terminal. Your local functions can connect to live Azure services, and you can debug your functions on your local computer using the full Functions runtime. You can even deploy a function app to your Azure subscription.


Do not mix local development with portal development in the same function app. When you create and publish functions from a local project, you should not try to maintain or modify project code in the portal.

Core Tools versions

There are two versions of Azure Functions Core Tools. The version you use depends on your local development environment, choice of language, and level of support required:

Unless otherwise noted, the examples in this article are for version 2.x.

Install the Azure Functions Core Tools

Azure Functions Core Tools includes a version of the same runtime that powers Azure Functions runtime that you can run on your local development computer. It also provides commands to create functions, connect to Azure, and deploy function projects.

Version 1.x

The original version of the tools uses the Functions 1.x runtime. This version uses the .NET Framework (4.7) and is only supported on Windows computers. Before you install the version 1.x tools, you must install NodeJS, which includes npm.

Use the following command to install the version 1.x tools:

npm install -g azure-functions-core-tools@v1

Version 2.x

Version 2.x of the tools uses the Azure Functions runtime 2.x that is built on .NET Core. This version is supported on all platforms .NET Core 2.x supports, including Windows, macOS, and Linux.


The following steps use npm to install Core Tools on Windows. You can also use Chocolatey. For more information, see the Core Tools readme.

  1. Install .NET Core 2.1 for Windows.

  2. Install Node.js, which includes npm. For version 2.x of the tools, only Node.js 8.5 and later versions are supported.

  3. Install the Core Tools package:

    npm install -g azure-functions-core-tools

MacOS with Homebrew

The following steps use Homebrew to install the Core Tools on macOS.

  1. Install .NET Core 2.1 for macOS.

  2. Install Homebrew, if it's not already installed.

  3. Install the Core Tools package:

    brew tap azure/functions
    brew install azure-functions-core-tools 

Linux (Ubuntu/Debian) with APT

The following steps use APT to install Core Tools on your Ubuntu/Debian Linux distribution. For other Linux distributions, see the Core Tools readme.

  1. Install .NET Core 2.1 for Linux.

  2. Register the Microsoft product key as trusted:

    curl | gpg --dearmor > microsoft.gpg
    sudo mv microsoft.gpg /etc/apt/trusted.gpg.d/microsoft.gpg
  3. Verify your Ubuntu server is running one of the appropriate versions from the table below. To add the apt source, run:

    sudo sh -c 'echo "deb [arch=amd64]$(lsb_release -cs)-prod $(lsb_release -cs) main" > /etc/apt/sources.list.d/dotnetdev.list'
    sudo apt-get update
    Linux distribution Version
    Ubuntu 18.04 bionic
    Ubuntu 17.10 artful
    Ubuntu 17.04 zesty
    Ubuntu 16.04/Linux Mint 18 xenial
  4. Install the Core Tools package:

    sudo apt-get install azure-functions-core-tools

Create a local Functions project

A functions project directory contains the files host.json and local.settings.json, along with subfolders that contain the code for individual functions. This directory is the equivalent of a function app in Azure. To learn more about the Functions folder structure, see the Azure Functions developers guide.

Version 2.x requires you to select a default language for your project when it is initialized, and all functions added use default language templates. In version 1.x, you specify the language each time you create a function.

In the terminal window or from a command prompt, run the following command to create the project and local Git repository:

func init MyFunctionProj

When you provide a project name, a new folder with that name is created and initialized. Otherwise, the current folder is initialized.
In version 2.x, when you run the command you must choose a runtime for your project. If you plan to develop JavaScript functions, choose node:

Select a worker runtime:

Use the up/down arrow keys to choose a language, then press Enter. The output looks like the following example for a JavaScript project:

Select a worker runtime: node
Writing .gitignore
Writing host.json
Writing local.settings.json
Writing C:\myfunctions\myMyFunctionProj\.vscode\extensions.json
Initialized empty Git repository in C:/myfunctions/myMyFunctionProj/.git/

func init supports the following options, which are version 2.x-only, unless otherwise noted:

Option Description
--csx Initializes a C# script (.csx) project. You must specify --csx in subsequent commands.
--docker Create a Dockerfile for a container using a base image that is based on the chosen --worker-runtime. Use this option when you plan to publish to a custom Linux container.
--force Initialize the project even when there are existing files in the project. This setting overwrites existing files with the same name. Other files in the project folder aren't affected.
--no-source-control -n Prevents the default creation of a Git repository in version 1.x. In version 2.x, the git repository isn't created by default.
--source-control Controls whether a git repository is created. By default, a repository isn't created. When true, a repository is created.
--worker-runtime Sets the language runtime for the project. Supported values are dotnet, node (JavaScript), and java. When not set, you are prompted to choose your runtime during initialization.


By default, version 2.x of the Core Tools creates function app projects for the .NET runtime as C# class projects (.csproj). These C# projects, which can be used with Visual Studio or Visual Studio Code, are compiled during testing and when publishing to Azure. If you instead want to create and work with the same C# script (.csx) files created in version 1.x and in the portal, you must include the --csx parameter when you create and deploy functions.

Register extensions

In version 2.x of the Azure Functions runtime, you have to explicitly register the binding extensions (binding types) that you use in your function app.

When you develop functions locally, you can install the extensions you need by using the Azure Functions Core Tools from the Terminal or from a command prompt.

After you have updated your function.json file to include all the bindings that your function needs, run the following command in the project folder.

func extensions install

The command reads the function.json file to see which packages you need, installs them, and rebuilds the extensions project. It adds any new bindings at the current version but does not update existing bindings. Use the --force option to update existing bindings to the latest version when installing new ones.

If you want to install a particular version of a package or you want to install packages before editing the function.json file, use the func extensions install command with the name of the package, as shown in the following example:

func extensions install --package Microsoft.Azure.WebJobs.ServiceBus --version <target_version>

Replace <target_version> with a specific version of the package, such as 3.0.0-beta5. Valid versions are listed on the individual package pages at

For more information, see Azure Functions triggers and bindings concepts.

Local settings file

The file local.settings.json stores app settings, connection strings, and settings for Azure Functions Core Tools. Settings in the local.settings.json file are only used by Functions tools when running locally. By default, these settings are not migrated automatically when the project is published to Azure. Use the --publish-local-settings switch when you publish to make sure these settings are added to the function app in Azure. Note that values in ConnectionStrings are never published. The file has the following structure:

  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "<language worker>",
    "AzureWebJobsStorage": "<connection-string>",
    "AzureWebJobsDashboard": "<connection-string>",
    "MyBindingConnection": "<binding-connection-string>"
  "Host": {
    "LocalHttpPort": 7071,
    "CORS": "*"
  "ConnectionStrings": {
    "SQLConnectionString": "<sqlclient-connection-string>"
Setting Description
IsEncrypted When set to true, all values are encrypted using a local machine key. Used with func settings commands. Default value is false.
Values Collection of application settings and connection strings used when running locally. These values correspond to app settings in your function app in Azure, such as AzureWebJobsStorage and AzureWebJobsDashboard. Many triggers and bindings have a property that refers to a connection string app setting, such as Connection for the Blob storage trigger. For such properties, you need an application setting defined in the Values array.
AzureWebJobsStorage is a required app setting for triggers other than HTTP. When you have the Azure storage emulator installed locally, you can set AzureWebJobsStorage to UseDevelopmentStorage=true and Core Tools uses the emulator. This is useful during development, but you should test with an actual storage connection before deployment.
Host Settings in this section customize the Functions host process when running locally.
LocalHttpPort Sets the default port used when running the local Functions host (func host start and func run). The --port command-line option takes precedence over this value.
CORS Defines the origins allowed for cross-origin resource sharing (CORS). Origins are supplied as a comma-separated list with no spaces. The wildcard value (*) is supported, which allows requests from any origin.
ConnectionStrings Do not use this collection for the connection strings used by your function bindings. This collection is only used by frameworks that typically get connection strings from the ConnectionStrings section of a configuration file, such as Entity Framework. Connection strings in this object are added to the environment with the provider type of System.Data.SqlClient. Items in this collection are not published to Azure with other app settings. You must explicitly add these values to the Connection strings collection of your function app settings. If you are creating a SqlConnection in your function code, you should store the connection string value in Application settings with your other connections.

The function app settings values can also be read in your code as environment variables. For more information, see the Environment variables section of these language-specific reference topics:

When no valid storage connection string is set for AzureWebJobsStorage and the emulator isn't being used, the following error message is shown:

Missing value for AzureWebJobsStorage in local.settings.json. This is required for all triggers other than HTTP. You can run 'func azure functionapp fetch-app-settings ' or specify a connection string in local.settings.json.

Get your storage connection strings

Even when using the storage emulator for development, you may want to test with an actual storage connection. Assuming you have already created a storage account, you can get a valid storage connection string in one of the following ways:

  • From the Azure portal. Navigate to your storage account, select Access keys in Settings, then copy one of the Connection string values.

    Copy connection string from Azure portal

  • Use Azure Storage Explorer to connect to your Azure account. In the Explorer, expand your subscription, select your storage account, and copy the primary or secondary connection string.

    Copy connection string from Storage Explorer

  • Use Core Tools to download the connection string from Azure with one of the following commands:

    • Download all settings from an existing function app:

      func azure functionapp fetch-app-settings <FunctionAppName>
    • Get the Connection string for a specific storage account:

      func azure storage fetch-connection-string <StorageAccountName>

      When you are not already signed in to Azure, you are prompted to do so.

Create a function

To create a function, run the following command:

func new

In version 2.x, when you run func new you are prompted to choose a template in the default language of your function app, then you are also prompted to choose a name for your function. In version 1.x, you are also prompted to choose the language.

Select a language: Select a template:
Blob trigger
Cosmos DB trigger
Event Grid trigger
HTTP trigger
Queue trigger
Service Bus Queue trigger
Service Bus Topic trigger
Timer trigger

Function code is generated in a subfolder with the provided function name, as you can see in the following queue trigger output:

Select a language: Select a template: Queue trigger
Function name: [QueueTriggerJS] MyQueueTrigger
Writing C:\myfunctions\myMyFunctionProj\MyQueueTrigger\index.js
Writing C:\myfunctions\myMyFunctionProj\MyQueueTrigger\
Writing C:\myfunctions\myMyFunctionProj\MyQueueTrigger\sample.dat
Writing C:\myfunctions\myMyFunctionProj\MyQueueTrigger\function.json

You can also specify these options in the command using the following arguments:

Argument Description
--csx (Version 2.x) Generates the same C# script (.csx) templates used in version 1.x and in the portal.
--language -l The template programming language, such as C#, F#, or JavaScript. This option is required in version 1.x. In version 2.x, do not use this option or choose a language that matches the worker runtime.
--name -n The function name.
--template -t Use the func templates list command to see the complete list of available templates for each supported language.

For example, to create a JavaScript HTTP trigger in a single command, run:

func new --template "Http Trigger" --name MyHttpTrigger

To create a queue-triggered function in a single command, run:

func new --template "Queue Trigger" --name QueueTriggerJS

Run functions locally

To run a Functions project, run the Functions host. The host enables triggers for all functions in the project:

func host start

The host command is only required in version 1.x.

func host start supports the following options:

Option Description
--build Build current project before running. Version 2.x and C# projects only.
--cert The path to a .pfx file that contains a private key. Only used with --useHttps. Version 2.x only.
--cors A comma-separated list of CORS origins, with no spaces.
--debug Starts the host with the debug port open so that you can attach to the func.exe process from Visual Studio Code or Visual Studio 2017. Valid values are VSCode and VS.
--language-worker Arguments to configure the language worker. Version 2.x only.
--nodeDebugPort -n The port for the node debugger to use. Default: A value from launch.json or 5858. Version 1.x only.
--password Either the password or a file that contains the password for a .pfx file. Only used with --cert. Version 2.x only.
--port -p The local port to listen on. Default value: 7071.
--pause-on-error Pause for additional input before exiting the process. Used only when launching Core Tools from an integrated development environment (IDE).
--script-root --prefix Used to specify the path to the root of the function app that is to be run or deployed. This is used for compiled projects that generate project files into a subfolder. For example, when you build a C# class library project, the host.json, local.settings.json, and function.json files are generated in a root subfolder with a path like MyProject/bin/Debug/netstandard2.0. In this case, set the prefix as --script-root MyProject/bin/Debug/netstandard2.0. This is the root of the function app when running in Azure.
--timeout -t The timeout for the Functions host to start, in seconds. Default: 20 seconds.
--useHttps Bind to https://localhost:{port} rather than to http://localhost:{port}. By default, this option creates a trusted certificate on your computer.

For a C# class library project (.csproj), you must include the --build option to generate the library .dll.

When the Functions host starts, it outputs the URL of HTTP-triggered functions:

Found the following functions:

Job host started
Http Function MyHttpTrigger: http://localhost:7071/api/MyHttpTrigger


When running locally, authentication isn't enforced for HTTP endpoints. This means that all local HTTP requests are handled as authLevel = "anonymous". For more information, see the HTTP binding article.

Passing test data to a function

To test your functions locally, you start the Functions host and call endpoints on the local server using HTTP requests. The endpoint you call depends on the type of function.


Examples in this topic use the cURL tool to send HTTP requests from the terminal or a command prompt. You can use a tool of your choice to send HTTP requests to the local server. The cURL tool is available by default on Linux-based systems. On Windows, you must first download and install the cURL tool.

For more general information on testing functions, see Strategies for testing your code in Azure Functions.

HTTP and webhook triggered functions

You call the following endpoint to locally run HTTP and webhook triggered functions:


Make sure to use the same server name and port that the Functions host is listening on. You see this in the output generated when starting the Function host. You can call this URL using any HTTP method supported by the trigger.

The following cURL command triggers the MyHttpTrigger quickstart function from a GET request with the name parameter passed in the query string.

curl --get http://localhost:7071/api/MyHttpTrigger?name=Azure%20Rocks

The following example is the same function called from a POST request passing name in the request body:

curl --request POST http://localhost:7071/api/MyHttpTrigger --data '{"name":"Azure Rocks"}'

You can make GET requests from a browser passing data in the query string. For all other HTTP methods, you must use cURL, Fiddler, Postman, or a similar HTTP testing tool.

Non-HTTP triggered functions

For all kinds of functions other than HTTP triggers and webhooks, you can test your functions locally by calling an administration endpoint. Calling this endpoint with an HTTP POST request on the local server triggers the function. You can optionally pass test data to the execution in the body of the POST request. This functionality is similar to the Test tab in the Azure portal.

You call the following administrator endpoint to trigger non-HTTP functions:


To pass test data to the administrator endpoint of a function, you must supply the data in the body of a POST request message. The message body is required to have the following JSON format:

    "input": "<trigger_input>"

The <trigger_input> value contains data in a format expected by the function. The following cURL example is a POST to a QueueTriggerJS function. In this case, the input is a string that is equivalent to the message expected to be found in the queue.

curl --request POST -H "Content-Type:application/json" --data '{"input":"sample queue data"}' http://localhost:7071/admin/functions/QueueTriggerJS

Using the func run command in version 1.x


The func run command is not supported in version 2.x of the tools. For more information, see the topic How to target Azure Functions runtime versions.

You can also invoke a function directly by using func run <FunctionName> and provide input data for the function. This command is similar to running a function using the Test tab in the Azure portal.

func run supports the following options:

Option Description
--content -c Inline content.
--debug -d Attach a debugger to the host process before running the function.
--timeout -t Time to wait (in seconds) until the local Functions host is ready.
--file -f The file name to use as content.
--no-interactive Does not prompt for input. Useful for automation scenarios.

For example, to call an HTTP-triggered function and pass content body, run the following command:

func run MyHttpTrigger -c '{\"name\": \"Azure\"}'

Viewing log files locally

When the Functions host runs locally, it writes logs to the following path:


On Windows, <DefaultTempDirectory> is the first found value of the TMP, TEMP, USERPROFILE environment variables, or the Windows directory. On MacOS or Linux, <DefaultTempDirectory> is the TMPDIR environment variable.


When the Functions host starts, it overwrites the existing file structure in the directory.

Publish to Azure

Core Tools supports two types of deployment, deploying function project files directly to your function app and deploying a custom Linux container, which is supported only in version 2.x. You must have already created a function app in your Azure subscription.

In version 2.x, you must have registered your extensions in your project before publishing. Projects that require compilation should be built so that the binaries can be deployed.

Project file deployment

The most common deployment method involves using Core Tools to package your function app project and deploy the package to your function app. You can optionally run your functions directly from the deployment package.

To publish a Functions project to a function app in Azure, use the publish command:

func azure functionapp publish <FunctionAppName>

This command publishes to an existing function app in Azure. An error occurs when the <FunctionAppName> doesn't exist in your subscription. To learn how to create a function app from the command prompt or terminal window using the Azure CLI, see Create a Function App for serverless execution.

The publish command uploads the contents of the Functions project directory. If you delete files locally, the publish command does not delete them from Azure. You can delete files in Azure by using the Kudu tool in the Azure portal.


When you create a function app in the Azure portal, it uses version 2.x of the Function runtime by default. To make the function app use version 1.x of the runtime, follow the instructions in Run on version 1.x.
You can't change the runtime version for a function app that has existing functions.

You can use the following publish options, which apply for both versions, 1.x and 2.x:

Option Description
--publish-local-settings -i Publish settings in local.settings.json to Azure, prompting to overwrite if the setting already exists. If you are using the storage emulator, you change the app setting to an actual storage connection.
--overwrite-settings -y Suppress the prompt to overwrite app settings when --publish-local-settings -i is used.

The following publish options are only supported in version 2.x:

Option Description
--publish-settings-only -o Only publish settings and skip the content. Default is prompt.
--list-ignored-files Displays a list of files that are ignored during publishing, which is based on the .funcignore file.
--list-included-files Displays a list of files that are published, which is based on the .funcignore file.
--zip Publish in Run-From-Zip package. Requires the app to have AzureWebJobsStorage setting defined.
--force Ignore pre-publishing verification in certain scenarios.
--csx Publish a C# script (.csx) project.
--no-build Skip building dotnet functions.
--dotnet-cli-params When publishing compiled C# (.csproj) functions, the core tools calls 'dotnet build --output bin/publish'. Any parameters passed to this will be appended to the command line.

Custom container deployment

Functions lets you deploy your function project in a custom Linux container. For more information, see Create a function on Linux using a custom image. Version 2.x of Core Tools supports deploying a custom container. Custom containers must have a Dockerfile. Use the --dockerfile option on func init.

func deploy

The following custom container deployment options are available:

Option Description
--registry The name of a Docker Registry the current user signed-in to.
--platform Hosting platform for the function app. Valid options are kubernetes
--name Function app name.
--max Optionally, sets the maximum number of function app instances to deploy to.
--min Optionally, sets the minimum number of function app instances to deploy to.
--config Sets an optional deployment configuration file.

Next steps

Azure Functions Core Tools is open source and hosted on GitHub.
To file a bug or feature request, open a GitHub issue.