---
title: ProExtensionPrincipalClass
framework: bundleresources
role: symbol
role_heading: Property List Key
path: bundleresources/information-property-list/nsextension/proextensionprincipalclass
---

# ProExtensionPrincipalClass

The name of the class with the principal implementation of your extension.

## Discussion

Discussion The Compressor app instantiates the class specified in the ProExtensionPrincipalClass key to convert source files to the output format your extension supports. Customize your extension code by adopting the following protocols in the implementation of this class: CompressorExtensionSettings CompressorExtensionColorSpaces CompressorExtensionSettingsOptional CompressorExtensionEncoder

## See Also

### Professional Video Applications

- [ProExtensionAttributes](bundleresources/information-property-list/nsextension/proextensionattributes.md)
- [ProExtensionPrincipalViewControllerClass](bundleresources/information-property-list/nsextension/proextensionprincipalviewcontrollerclass.md)
- [ProExtensionUUID](bundleresources/information-property-list/nsextension/proextensionuuid.md)