How to Filter an Array in Power Automate

Filter array keeps the items of an array that match a condition and drops the rest. Give it the array in From, and a condition that uses item(), the item being checked. The example drops one person's email from a list of approvers.

Microsoft's data operations article says: Use the Data Operation - Filter array action to reduce the number of objects in an array to a subset that matches the criteria you provide.

The example is the approval flow of the Overtime Timesheet app. A department's approver can also log overtime, and shouldn't approve their own, so the flow removes the person who logged the entry from the department's approvers.

Prerequisites

• An array. Here, the list of approver emails from a Select action, Approver emails (How to Pick One Field from Each Item with Select in Power Automate).

Step 1: Add Filter Array

Add an action, search for Filter array, and choose it under Data Operation. I named it Approvers other than the employee.

Step 2: Choose the Array

In From, pick the array from dynamic content: Output of Approver emails:

Step 3: Write the Condition

The condition compares each email with the email of the person who created the entry, from the trigger, and keeps it when they're not the same. In basic mode, it's three parts:

Left	Operator	Right
toLower(item())	is not equal to	toLower(triggerOutputs()?['body/Author/Email'])

Insert each side as an expression (How to Add an Expression in Power Automate):

Edit in advanced mode shows the same condition as one expression:

Approvers other than the employee → Filter Query (advanced mode)

@not(equals(toLower(item()), toLower(triggerOutputs()?['body/Author/Email'])))

How it reads:

• item() is the email being checked; Select produced plain text, so there's no field to read.
• toLower() makes both sides lowercase. Microsoft's functions reference says it will Return a string in lowercase format. The address is stored in two places, the department's Approvers and the entry's Created By, and lowercase on both sides means the comparison doesn't depend on how either was capitalised. The reference doesn't say whether equals() compares text case-sensitively, so the flow doesn't rely on it either way.
• equals() is true when both are the same, and not() turns that around, so the item stays when they're different.

In Code view, the action's from and where:

The Result

Someone else logged it. Maya Patel's entry in Radiology, whose approver is Daniel Brooks: Daniel's email stayed in the array:

The approver logged it. Daniel's own entry in Radiology: his email was dropped, and nothing was left:

An empty result is a normal outcome, and the next step checks for it (How to Count the Items in an Array in Power Automate with length()).

Common Mistakes

Mistake	What happens	Do this instead
item()?['Email'] after a Select in text mode	The items are text, with no fields	item()
Comparing addresses as they're stored	The result depends on capitalisation, which the docs don't settle	toLower() on both sides
is equal to where you meant to remove	Keeps only the matching item	is not equal to
Expecting at least one item	An empty array goes on to the next steps	Check with length() first

Troubleshooting

Symptom	Likely cause	Fix
The person is still in the result	The two addresses differ	Compare them in a run's outputs
Everything is dropped	The condition is the wrong way round	Swap is equal to and is not equal to
An empty output	Nothing matched	Expected, when nothing should match

FAQ

Can I use several conditions?

In advanced mode, combine them with and() or or() in one expression.

Does Filter array change the original array?

No. It returns a new array; the one in From stays as it was.

Conclusion

Filter array keeps the items for which its condition is true: From the array, then a condition on item(). With @not(equals(toLower(item()), toLower(...))), it dropped the person who logged the overtime from the approvers, and an empty result told the flow to ask their manager.

Additional Resources

• Use data operations: Filter array: the action.
• Reference guide to functions in expressions: item(), toLower(), equals() and not().

Related

• How to Pick One Field from Each Item with Select in Power Automate
• How to Count the Items in an Array in Power Automate with length()
• How to Join an Array into Text in Power Automate
• How to Add an Expression in Power Automate