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iot-hub-devguide-c2d-guidance.md

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title Azure IoT Hub cloud-to-device options
description This article provides guidance on when to use direct methods, device twin's desired properties, or cloud-to-device messages for cloud-to-device communications.
author cwatson-cat
ms.author cwatson
ms.service azure-iot-hub
ms.topic concept-article
ms.date 05/22/2025
ms.custom
amqp
mqtt
Role: Cloud Development
Role: IoT Device

Cloud-to-device communications guidance

This article helps you choose the appropriate cloud-to-device communication option in Azure IoT Hub based on your scenario requirements. IoT Hub supports three primary options for cloud-to-device communication: direct methods, device twin's desired properties, and cloud-to-device messages.

Ways to communicate from cloud to device

IoT Hub provides three options for device apps to expose functionality to a back-end app:

  • Direct methods for communications that require immediate confirmation of the result. Direct methods are often used for interactive control of devices such as turning on a fan.

  • Device twin's desired properties for long-running commands intended to put the device into a certain desired state. For example, set the telemetry send interval to 30 minutes.

  • Cloud-to-device messages for one-way notifications to the device app.

To learn how Azure IoT Plug and Play uses these options to control IoT Plug and Play devices, see IoT Plug and Play service developer guide.

[!INCLUDE iot-hub-basic]

Comparison of cloud-to-device communication options

The following table compares the various cloud-to-device communication options in IoT Hub based on common factors.

Factor Direct methods Device twin's desired properties Cloud-to-device messages
Scenario Commands that require immediate confirmation, such as turning on a fan. Long-running commands intended to put the device into a certain desired state. For example, set the telemetry send interval to 30 minutes. One-way notifications to the device app.
Data flow Two-way. The device app can respond to the method right away. The solution back end receives the outcome contextually to the request. One-way. The device app receives a notification with the property change. One-way. The device app receives the message.
Durability Disconnected devices aren't contacted. The solution back end is notified that the device isn't connected. Property values are preserved in the device twin. Device will read it at next reconnection. Property values are retrievable with the IoT Hub query language. IoT Hub can retain messages for up to 48 hours.
Targets Single device using deviceId, or multiple devices using jobs. Single device using deviceId, or multiple devices using jobs. Single device by deviceId.
Size Maximum direct method payload size is 128 KB for the request and 128 KB for the response. Maximum desired properties size is 32 KB. Up to 64-KB messages.
Frequency High. For more information, see IoT Hub quotas and throttling. Medium. For more information, see IoT Hub quotas and throttling. Low. For more information, see IoT Hub quotas and throttling.
Protocol Available using MQTT or AMQP. Available using MQTT or AMQP. Available on all protocols. Device must poll when using HTTPS.

Learn how to use direct methods, desired properties, and cloud-to-device messages in the following tutorials: