# Building a properties panel

This section describes the basic principles behind defining and using properties in visualization extensions.

Properties offers you a way of customizing the behavior of visualization extensions in the same way as they would control native Qlik Sense visualizations. A developer can use a programmatic interface to define properties that are displayed in the properties panel exactly the same way as they are in the native Qlik Sense visualizations.

## The properties panel

Properties are structured hierarchically which is depicted in properties panel accordion below.

![Example properties panel, with Sections at the top, Header at the top of the currently opened Section, and Items below the Header](https://help.qlik.com/en-US/sense-developer/May2026/Subsystems/Extensions/Content/Resources/Images/ui-extension-get-started-08.png)

* A: Sections

* B: Header

* C: Items

## Defining the properties panel

Properties are added by defining them in the definition property in the JavaScript file. There are two ways of defining properties:

* Reusing existing, built-in, properties
* Create custom properties