Bring your own functions to Azure Static Web Apps

Azure Static Web Apps APIs are supported by two possible configurations: managed functions and bring your own functions. See the overview for details between the two configurations.

This article demonstrates how to link an existing Azure Functions app to an Azure Static Web Apps resource.

Note

Bring your own functions is only available in the Azure Static Web Apps Standard plan.

Example

Consider an existing Azure Functions app that exposes an endpoint via the following location.

https://my-functions-app.azurewebsites.net/api/getProducts

Once linked, you can access that same endpoint through the api path from your static web app, as shown in this example URL.

https://red-sea-123.azurestaticapps.net/api/getProducts

Both endpoint URLs point to the same function.

Before you associate an existing Functions app, you first need to adjust to configuration of your static web app.

  1. Set api_location value to an empty string ("") in the workflow configuration file.

  2. Open your Static Web Apps instance in the Azure portal.

  3. From the Settings menu, select APIs.

  4. From the Production row, select Link to open the Link new Backend window.

    Enter the following settings.

    Setting Value
    Backed resource type Select Function App.
    Subscription Select your Azure subscription name.
    Resource name Select the Azure Functions app name.
  5. Select the Link button.

The Azure Functions app is now mapped to the /api route of your static web app.

Important

Make sure to set the api_location value to an empty string ("") in the workflow configuration file before you link an existing Functions application.

Deployment

You're responsible for setting up a deployment workflow for your Azure Functions app.

Security constraints

  • Authentication and authorization: If authentication and authorization policies aren't already set up on your existing Functions app, then the static web app has exclusive access to the API. To make your Functions app accessible to other applications, add another identity provider or change the security settings to allow unauthenticated access.

    Note

    If you enable authentication and authorization in your linked Functions app, it must use Azure App Service Authentication and authorization provider version 2.

  • Required public accessibility: An existing Functions app needs to not apply the following security configurations.

    • Restricting the IP address of the Functions app.
    • Restricting traffic through private link or service endpoints.
  • Function access keys: If your function requires an access key, then you must provide the key with calls from the static app to the API.

Restrictions

  • Only one Azure Functions app is available to a single static web app.
  • The api_location value in the workflow configuration must be set to an empty string.
  • Only supported in the Static Web Apps production environment.
  • While your Azure Functions app may respond to various triggers, the static web app can only access functions via Http endpoints.

Next steps