---
title: "Filter a List by Another List"
slug: "form-builder-filter-a-list-by-another-list"
updated: 2026-10-28T14:24:51Z
published: 2026-10-28T14:24:51Z
canonical: "help.quickbase.com/form-builder-filter-a-list-by-another-list"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.quickbase.com/llms.txt
> Use this file to discover all available pages before exploring further.

# 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.

![](https://cdn.document360.io/dd260e4e-10bb-4b66-8fb3-5504c272b904/Images/Documentation/image-1792767598528.png?sv=2026-02-06&spr=https&st=2026-10-30T02%3A44%3A48Z&se=2026-10-30T03%3A44%3A48Z&sr=c&sp=r&sig=FP72EEOU2hh9dCCZrK90wLuCoc1fQNf6r6MuUJkwRCA%3D)

*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

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

![](https://cdn.document360.io/dd260e4e-10bb-4b66-8fb3-5504c272b904/Images/Documentation/filterlist-01-first-list-field-key(1).png?sv=2026-02-06&spr=https&st=2026-10-30T02%3A44%3A48Z&se=2026-10-30T03%3A44%3A48Z&sr=c&sp=r&sig=FP72EEOU2hh9dCCZrK90wLuCoc1fQNf6r6MuUJkwRCA%3D)

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

> [!NOTE]
> 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

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

![](https://cdn.document360.io/dd260e4e-10bb-4b66-8fb3-5504c272b904/Images/Documentation/filterlist-02-filter-keys.png?sv=2026-02-06&spr=https&st=2026-10-30T02%3A44%3A48Z&se=2026-10-30T03%3A44%3A48Z&sr=c&sp=r&sig=FP72EEOU2hh9dCCZrK90wLuCoc1fQNf6r6MuUJkwRCA%3D)

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

> [!WARNING]
> 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

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

![](https://cdn.document360.io/dd260e4e-10bb-4b66-8fb3-5504c272b904/Images/Documentation/image-1792767759577.png?sv=2026-02-06&spr=https&st=2026-10-30T02%3A44%3A48Z&se=2026-10-30T03%3A44%3A48Z&sr=c&sp=r&sig=FP72EEOU2hh9dCCZrK90wLuCoc1fQNf6r6MuUJkwRCA%3D)

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

1. 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](/fastfield/docs/en/form-builder-how-do-i-add-values-to-my-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**

![](https://cdn.document360.io/dd260e4e-10bb-4b66-8fb3-5504c272b904/Images/Documentation/filterlist-05-data-table-filter-key-column.png?sv=2026-02-06&spr=https&st=2026-10-30T02%3A44%3A48Z&se=2026-10-30T03%3A44%3A48Z&sr=c&sp=r&sig=FP72EEOU2hh9dCCZrK90wLuCoc1fQNf6r6MuUJkwRCA%3D)

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

## What's next

- [Filter a list based on user](/fastfield/docs/en/form-builder-filter-a-list-based-on-user)
- [Use lookup mappings to auto-populate fields with data](/fastfield/docs/en/form-builder-use-lookup-mappings-to-auto-populate-fields-with-data)
- [List selector](/fastfield/docs/en/form-builder-list-selector)