Compose in Power Automate

The Compose action in Power Automate is a simple yet powerful tool that allows you to store and manipulate data during a flow run. Whether you’re combining strings, preparing outputs, or storing JSON for further use, Compose offers a clean and efficient way to manage data.

In this guide, you’ll learn how to use Compose in Power Automate effectively — with real-world examples, best practices, and expert insights to help you build better flows.

📑 Table of Contents

• What Is the Compose Action in Power Automate?
• Why Use Compose in Power Automate?
• Key Features of the Compose Action
• Real-World Use Cases for Compose
• Compose vs Variables
• Using Expressions with Compose
• Best Practices
• Common Pitfalls
• Summary

🧩 What Is the Compose Action in Power Automate?

The Compose action is used to output a value without storing it in memory like a variable. It is typically used for:

• Testing and debugging expressions
• Formatting or transforming data
• Temporarily storing calculated values
• Reusing outputs multiple times in a flow

It doesn’t “do” anything — it just holds a value for use elsewhere in your flow.

💡 Why Use Compose in Power Automate?

You should use Compose in Power Automate when:

• You want to simplify a complex expression
• You need to reuse a calculated result multiple times
• You want to visualize or debug dynamic values
• You need to structure JSON for use in HTTP or custom connectors
• You’re chaining transformations like concat(), formatDateTime(), or join()

✨ Key Features of the Compose Action

💼 Real-World Use Cases for Compose in Power Automate

Here are practical scenarios where Compose is ideal:

🔹 Use Case 1: Format a Date

formatDateTime(utcNow(), 'MMMM dd, yyyy')

Use Compose to format the current date, and then reference it in email or Teams message.

🔹 Use Case 2: Combine Strings

concat('Customer Name: ', triggerOutputs()?['body/CustomerName'])

This output can be reused in a condition or message action.

🔹 Use Case 3: Clean Up Data Before Output

Use Compose to trim whitespace or convert values:

trim(triggerOutputs()?['body/Comment'])

🔹 Use Case 4: Prepare JSON for HTTP Request

{
  "id": "@{outputs('Get_item')?['body/ID']}",
  "name": "@{outputs('Get_item')?['body/Title']}"
}

Build structured JSON in a Compose step and send it via HTTP.

🔁 Compose vs Initialize Variable

Best Practice: Use Compose when you don’t need to change the value after setting it.

🧠 Using Expressions with Compose in Power Automate

You can write Power Automate expressions directly in the Compose action using the expression editor.

Popular examples:

• String manipulation:

  toUpper(triggerOutputs()?['body/Name'])
  

• Math calculation:

  add(10, 5)
  

• Check for nulls:

  coalesce(triggerOutputs()?['body/Email'], 'No email provided')
  

• Create arrays:

  createArray('Apples', 'Bananas', 'Oranges')
  

✅ Best Practices for Using Compose in Power Automate

• ✅ Name your Compose actions clearly (e.g., “FormatDate” or “FullName”)
• ✅ Reuse Compose outputs instead of retyping expressions
• ✅ Keep Compose actions grouped near their usage
• ✅ Use Compose for debugging dynamic content before you finalize the flow
• ✅ Store JSON responses in Compose for easier mapping later

⚠️ Common Pitfalls to Avoid

📘 Summary: Mastering Compose in Power Automate

The Compose action in Power Automate is a low-overhead way to store and reuse dynamic values, test expressions, and prepare outputs. It plays a crucial role in building scalable and maintainable flows.

Use Compose to:

• Format and transform data
• Store calculated outputs
• Simplify complex expressions
• Structure JSON or arrays