Azure Functions HTTP output bindings

HTTP-triggered functions use HTTP output to respond to the HTTP request sender. In most languages, this output is represented as an HTTP output binding. In Go, HTTP responses are written directly with the http.ResponseWriter passed to your HTTP trigger handler rather than with a separate output binding configuration.

The default return value for an HTTP-triggered function is:

• HTTP 204 No Content with an empty body in Functions 2.x and higher
• HTTP 200 OK with an empty body in Functions 1.x

Attribute

Isolated worker model

A return value attribute isn't required when using HttpResponseData. However, when using a ASP.NET Core integration and multi-binding output objects, the [HttpResultAttribute] attribute should be applied to the object property. The attribute takes no parameters. To learn more, see Usage.

In-process model

Important

Support will end for the in-process model on November 10, 2026. We highly recommend that you migrate your apps to the isolated worker model for full support.

A return value attribute isn't required for a class library. C# script instead uses a function.json configuration file as described in the C# scripting guide. To learn more, see Usage.

Annotations

In the Java functions runtime library, use the HttpOutput annotation to define an output variable other than the default variable returned by the function. This annotation supports the following settings:

• dataType
• name

Important

This article uses tabs to support multiple versions of the Node.js programming model. The v4 model is generally available and is designed to have a more flexible and intuitive experience for JavaScript and TypeScript developers. For more details about how the v4 model works, refer to the Azure Functions Node.js developer guide. To learn more about the differences between v3 and v4, refer to the migration guide.

Configuration

Model v4

The options object passed to the output.http() method currently doesn't support any properties for model v4.

Model v3

The following table explains the binding configuration properties that you set in the function.json file.

Property	Description
type	Must be set to http.
direction	Must be set to out.
name	The variable name used in function code for the response, or $return to use the return value.

Configuration

The following table explains the binding configuration properties that you set in the function.json file.

Property	Description
type	Must be set to http.
direction	Must be set to out.
name	The variable name used in function code for the response, or $return to use the return value.

In Go, HTTP output is handled through the standard http.ResponseWriter that's passed to your HTTP trigger handler. You write your response directly using the writer. No separate output binding configuration is needed.

func hello(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    w.WriteHeader(http.StatusOK)
    fmt.Fprintf(w, `{"message": "Hello from Go!"}`)
}

Usage

To send an HTTP response, use the language-standard response patterns.

In .NET, the response type depends on the C# mode:

Isolated worker model

The HTTP triggered function returns an object of one of the following types:

• IActionResult¹ (or Task<IActionResult>)
• HttpResponse¹ (or Task<HttpResponse>)
• HttpResponseData (or Task<HttpResponseData>)
• JSON serializable types representing the response body for a 200 OK response.

¹ This type is only available when using ASP.NET Core integration.

When one of these types is used as part of multi-binding output objects, the [HttpResult] attribute should be applied to the object property. The attribute takes no parameters.

In-process model

The HTTP triggered function returns a type of IActionResult or Task<IActionResult>.

For Java, use an HttpResponseMessage.Builder to create a response to the HTTP trigger. To learn more, see HttpRequestMessage and HttpResponseMessage.

For example responses, see the trigger examples.

Next steps

• Run a function from an HTTP request