Triggers and bindings in Azure Functions (2024)

In this article, you learn the high-level concepts surrounding functions triggers and bindings.

Triggers cause a function to run. A trigger defines how a function is invoked and a function must have exactly one trigger. Triggers can also pass data into your function, as you would with method calls.

Binding to a function is a way of declaratively connecting your functions to other resources; bindings either pass data into your function (an input binding) or enable you to write data out from your function (an output binding) using binding parameters. Your function trigger is essentially a special type of input binding.

You can mix and match different bindings to suit your function's specific scenario. Bindings are optional and a function might have one or multiple input and/or output bindings.

Triggers and bindings let you avoid hardcoding access to other services. Your function receives data (for example, the content of a queue message) in function parameters. You send data (for example, to create a queue message) by using the return value of the function.

Consider the following examples of how you could implement different functions.

^* Represents different queues

These examples aren't meant to be exhaustive, but are provided to illustrate how you can use triggers and bindings together. For a more comprehensive set of scenarios, see Azure Functions scenarios.

Trigger and binding definitions

Triggers and bindings are defined differently depending on the development language. Make sure to select your language at the top of the article.

Bindings can be either input or output bindings. Not all services support both input and output bindings. See your specific binding extension for specific bindings code examples.

This example shows an HTTP triggered function with an output binding that writes a message to an Azure Storage queue.

[Function("HttpExample")]public static MultiResponse Run([HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequestData req, FunctionContext executionContext){

public class MultiResponse{ [QueueOutput("outqueue",Connection = "AzureWebJobsStorage")] public string[] Messages { get; set; } public HttpResponseData HttpResponse { get; set; }}

@FunctionName("HttpExample")public HttpResponseMessage run( @HttpTrigger(name = "req", methods = {HttpMethod.GET, HttpMethod.POST}, authLevel = AuthorizationLevel.ANONYMOUS) HttpRequestMessage<Optional<String>> request, @QueueOutput(name = "msg", queueName = "outqueue", connection = "AzureWebJobsStorage") OutputBinding<String> msg, final ExecutionContext context) { context.getLogger().info("Java HTTP trigger processed a request.");

This example is an HTTP triggered function that creates a queue item for each HTTP request received.

const { app, output } = require('@azure/functions');const queueOutput = output.storageQueue({ queueName: 'outqueue', connection: 'MyStorageConnectionAppSetting',});app.http('httpTrigger1', { methods: ['GET', 'POST'], authLevel: 'anonymous', extraOutputs: [queueOutput], handler: async (request, context) => { const body = await request.text(); context.extraOutputs.set(queueOutput, body); return { body: 'Created queue item.' }; },});

import { app, HttpRequest, HttpResponseInit, InvocationContext, output } from '@azure/functions';const queueOutput = output.storageQueue({ queueName: 'outqueue', connection: 'MyStorageConnectionAppSetting',});export async function httpTrigger1(request: HttpRequest, context: InvocationContext): Promise<HttpResponseInit> { const body = await request.text(); context.extraOutputs.set(queueOutput, body); return { body: 'Created queue item.' };}app.http('httpTrigger1', { methods: ['GET', 'POST'], authLevel: 'anonymous', extraOutputs: [queueOutput], handler: httpTrigger1,});

 { "authLevel": "function", "type": "httpTrigger", "direction": "in", "name": "Request", "methods": [ "get", "post" ] }, { "type": "http", "direction": "out", "name": "Response" }, { "type": "queue", "direction": "out", "name": "msg", "queueName": "outqueue", "connection": "AzureWebJobsStorage" } ]}

app = func.FunctionApp(http_auth_level=func.AuthLevel.ANONYMOUS)@app.route(route="HttpExample")@app.queue_output(arg_name="msg", queue_name="outqueue", connection="AzureWebJobsStorage")def HttpExample(req: func.HttpRequest, msg: func.Out [func.QueueMessage]) -> func.HttpResponse: logging.info('Python HTTP trigger function processed a request.')

Add bindings to a function

You can connect your function to other services by using input or output bindings. Add a binding by adding its specific definitions to your function. To learn how, see Add bindings to an existing function in Azure Functions.

Supported bindings

This table shows the bindings that are supported in the major versions of the Azure Functions runtime:

Notes:

1. Support will end for version 1.x of the Azure Functions runtime on September 14, 2026. We highly recommend that you migrate your apps to version 4.x for full support.
2. Starting with the version 2.x runtime, all bindings except HTTP and Timer must be registered. See Register binding extensions.
3. Triggers aren't supported in the Consumption plan. Requires runtime-driven triggers.
4. Supported in Kubernetes, IoT Edge, and other self-hosted modes only.

For information about which bindings are in preview or are approved for production use, see Supported languages.

Specific binding extension versions are only supported while the underlying service SDK is supported. Changes to support in the underlying service SDK version affect the support for the consuming extension.

Bindings code examples

Use the following table to find more examples of specific binding types that show you how to work with bindings in your functions. First, choose the language tab that corresponds to your project.

Custom bindings

You can create custom input and output bindings. Bindings must be authored in .NET, but can be consumed from any supported language. For more information about creating custom bindings, see Creating custom input and output bindings.

Related content

• Binding expressions and patterns
• How to register a binding expression
• Testing:
  • Strategies for testing your code in Azure Functions
  • Manually run a non HTTP-triggered function
• Handling binding errors