$loadedExtensions = \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::getLoadedExtensionListArray(); print_r($loadedExtensions);
if (\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::isLoaded('my_extension')) { // do something if the extension is loaded }This example checks if the extension with the key "my_extension" is loaded in TYPO3 using the isLoaded function. Package library: TYPO3\CMS\Core\Utility\ExtensionManagementUtility is part of the TYPO3 CMS core library.