How to Use Append to String and Append to Array Variable in the Flow

Append to String Variable

The "Append to string variable" action in Power Automate is used to add more text to an existing string variable without overwriting its current value. Think of it as taking a note and writing extra text at the end rather than starting fresh.

Key Points

Only works on variables of type string.
You cannot use it on uninitialized variables—you need to create a string variable first.
It is useful for building dynamic text, creating logs, or collecting multiple items into a single text value.

Step 1: Initialize the String Variable

Before appending, you need a string variable:

Add Initialize variable action.

Set:

Name: MyString
Type: String
Value: "Hello"

Step 2: Append to the String Variable

Add Append to string variable action.

Set:

Name: MyString
Value: " World!"

This will add " World!" to the existing "Hello" value.

Step 3: Using the String

You can now use the variable in emails, messages, or logs. For example:

Add Compose action and use MyString.

Output:

Hello World!

Full Example Flow

Scenario: Collecting names of attendees in a list.

Initialize variable – Attendees (String) → empty ""
Apply to each attendee in your list:
- Append to string variable → Value:

@{items('Apply_to_each')['Name']},

Compose / Send email → Attendees

Output might be:

Person1, Person2, Person3,

Scenario: Collect Email Addresses from a SharePoint List

Suppose you have a SharePoint list of employees, and you want to collect all email addresses into a single string separated by commas.

Step 1: Initialize the String Variable

Action: Initialize variable

Name: AllEmails
Type: String
Value: "" (empty)

Step 2: Get Items from SharePoint

Action: Get items

Site Address: Your SharePoint site
List Name: Employees

This retrieves all employee records.

Step 3: Apply to Each Item

Action: Apply to each → value from Get items

Inside this loop:

Append to string variable

Set:

Name: AllEmails
Value:

@{items('Apply_to_each')['Email']},

This takes each employee's email and adds it to the AllEmails string, separated by commas.

Step 4: Use the Combined String

Action: Send an email

To:

AllEmails

Result:

If your SharePoint list has these emails:

[email protected]
[email protected]
[email protected]

Then after the flow runs, AllEmails will be:

[email protected], [email protected], [email protected],

You can then use a substring() expression to remove the trailing comma if needed:

substring(variables('AllEmails'), 0, sub(length(variables('AllEmails')), 2))

Tips

Always initialize the variable first.
Use Append when building a single combined string.
Use Set variable if you want to replace the value entirely.
To remove trailing separators (like the last comma), you can use substring() or trim() in expressions.

Append to Array Variable

Append to array variable in Microsoft Power Automate is an action used to add a new value or item to an existing array variable during a flow. It helps collect multiple pieces of data into a single list as the workflow runs.

1️⃣ Create the Array Variable First

Before you can append to an array, you must initialize it.

Add action Initialize variable

Configure:

Name: MyArray
Type: Array
Value:

[]

2️⃣ Add the Append to Array Variable Action

Click New step
Search for Append to array variable

Configure:

Name: MyArray
Value: value you want to add

Example:

{
  "Name": "John",
  "Age": 30
}

Each time the flow runs this step, the item gets added to the array.

3️⃣ Example Result

After multiple appends, the array becomes:

[
  { "Name": "John", "Age": 30 },
  { "Name": "Sara", "Age": 28 },
  { "Name": "Mike", "Age": 35 }
]

4️⃣ Common Use Cases

Collect items inside a loop
Build a JSON array
Combine results from multiple actions
Prepare data for API calls

Typical pattern inside a loop:

Initialize Array
      ↓
Apply to each
      ↓
Append to array variable
      ↓
Use final array

Collect Emails from a SharePoint List

Scenario

You have a SharePoint Employee List like this:

Name	Email
Person1	[email protected]
Person2	[email protected]
Person3	[email protected]

Goal:

Create a flow that collects all emails into one array and later sends an email to them.

Step 1 — Trigger

Create a flow with a trigger.

Example:

Manual trigger
When an item is created

Step 2 — Get Items from SharePoint

Add action:

Get items

Settings:

Site Address: Company Site
List Name: Employee List

Output example:

[
 {Name:"Person1", Email:"[email protected]"},
 {Name:"Person2", Email:"[email protected]"},
 {Name:"Person3", Email:"[email protected]"}
]

Step 3 — Initialize Array

Add action Initialize variable

Field	Value
Name	EmailArray
Type	Array
Value	[]

Current array:

[]

Step 4 — Apply to Each

Add Apply to each

Input:

value (from Get Items)

This loops through each employee.

Step 5 — Append Email to Array

Inside the loop add Append to array variable

Field	Value
Name	EmailArray
Value	Email

Expression example:

items('Apply_to_each')?['Email']

Step 6 — Result After Loop

Array becomes:

[
 "[email protected]",
 "[email protected]",
 "[email protected]"
]

Step 7 — Use the Array

Now you can use the array in Send an Email action.

Example:

To field:

join(variables('EmailArray'), ';')

Result:

[email protected];[email protected];[email protected]

Final Flow Structure

Trigger
   ↓
Get Items (SharePoint)
   ↓
Initialize Array (EmailArray)
   ↓
Apply to Each
      ↓
Append to Array Variable
   ↓
Send Email

What Append to Array Did

It collected emails like this:

[]
↓
["[email protected]"]
↓
["[email protected]","[email protected]"]
↓
["[email protected]","[email protected]","[email protected]"]

Conclusion

'Append to String' and 'Append to Array' in Power Automate lets you easily build dynamic text and collections, making your flows more flexible and powerful.