Flow and SharePoint: How to Check for Empty Fields

I have found quite a few people asking about empty fields and how to check in Microsoft Flow that these fields are empty. In this post, I'm going through the options.

I'm going to start my Flow with a trigger When an item is created or modified. I'm selecting my testlist and I'm putting in a Condition to test a text field called Description.

Additionally I'm creating a condition that uses the empty expression.

And finally I create a condition that uses the expression null

Then I create an item and my flow will start. Would you expect that each of these conditions gives you the same result? Well have a look at the output below:

Only the last condition actually works, so why is that?

To explain this, I'm going to have a look at the SharePoint REST api. by visiting the following URL in my browser:

https://mytenant.sharepoint.com/_api/web/lists/getbytitle('testlist')/items(14)

This collects item 14 from my testlist.

When investigating the output from the REST API, you can see that the value of the description field isn't an empty string but it is set to null instead. Hence all the string operation will not work.