# Preview dialog

[](https://help.qlik.com/en-US/sense-developer/Subsystems/Extensions/Content/Sense_Extensions/Overview/preview-dialog.htm)The content of the QEXT file defines what is visible when previewing the visualization extension in Qlik Sense.

This is what you define in the QEXT file:

```
{
	"name" : "Hello World",
	"description" : "Hello World example",
	"icon" : "extensions",
	"preview": "helloworld.png",
	"type" : "visualization"
}
```

This is how it is displayed in the Preview dialog:

![Preview dialog displaying name and icon definitions in the extension list, and name, preview and description definitions in the preview dialog](https://help.qlik.com/en-US/sense-developer/May2026/Subsystems/Extensions/Content/Resources/Images/dr-extension-preview-dialog.png)

Legend:

* A: name definition.
* B: preview definition.
* C: description definition.
* D: icon definition.

## Learn more

* [Working with the meta data](https://help.qlik.com/en-US/sense-developer/May2026/Subsystems/Extensions/Content/Sense_Extensions/Overview/qext-file-overview.htm)
* [Custom preview images](https://help.qlik.com/en-US/sense-developer/May2026/Subsystems/Extensions/Content/Sense_Extensions/Howtos/add-preview-image.htm)
* [Defining the icon](https://help.qlik.com/en-US/sense-developer/May2026/Subsystems/Extensions/Content/Sense_Extensions/Howtos/add-custom-icon.htm)