Filter a List by Another List

A filtered list shows only the choices that match an earlier answer, so users see fewer items to choose from. This article covers how to link 2 lists in the Form Builder so the first selection filters the second.

How list filtering works

Filtering links 2 fields with 2 keys:

Key	Where you set it	What it does
Filter Key	On each choice in the second list	Names the value from the first list that the choice belongs to
Field Filter Key	In the second list's field settings	Names the field key of the first list

For example, a form asks for a Location first. The Employee list then shows only the employees who work at that location. Each employee's Filter Key is their location, and the Employee list's Field Filter Key is the Location field's key.

Until users answer the first list, the second list is empty. It asks them to answer the first list.

*The form preview with the Employee list asking the user to select a value from Location first*

You can filter List, Global List, Lookup List, and DataTable List fields. Option List fields don't have a Field Filter Key.

Set up the first list

In the Form Builder, add a List field for the first question, for example Location.
Under List Options, add the choices, for example North Yard and South Yard.
Copy the value in Field Key. You need it for the second list.

*Field Settings for the Location list, with its Field Key and 2 choices*

Tip
To see every field key on the canvas, select Settings in the bottom toolbar. Then turn on Show Fieldkeys.

Add filter keys to the second list

Add a List field for the second question, for example Employee.
Under List Options, select Advanced Options.
For each choice, enter the Name. In Filter Key, enter the value of the matching choice in the first list.
Select Add after each choice, then select Close.

*Advanced List Options for the Employee list, with North Yard or South Yard as each employee's Filter Key*

Important
The Filter Key must match the first list's choice value exactly, not its name. If a choice in the first list has a separate value, use that value. Letter case doesn't matter.

Link the second list to the first

Select the second list on the canvas.
In Field Filter Key, paste the field key of the first list.

*Field Settings for the Employee list, with the Location field key entered as the Field Filter Key*

Select Save Draft, then select Publish when you're ready for users to see the change.

When users select a location, the Employee list shows only the employees with that Filter Key.

Filter Global Lists, Lookup Lists, and Data Tables

These fields get their choices from a list outside the form. The filter keys come from that list.

Global List: Add the filter keys in the list's Filter Value column. Learn more about adding values to your list
Lookup List and DataTable List: Choose the column that holds the filter keys. In the field settings, select View / Edit List or View / Edit Data Table. Then select the column in Filter Key

*The Equipment Data Table with the Customer Name column chosen as the Filter Key*

Then enter the first list's field key in the field's Field Filter Key, the same as for a List field.

Note
The Assistant can add the lists and their choices, but it can't set filter keys. Set them in Field Settings.