System and Local extensions

The files for an extension are located in a folder named by the extension key . The location of this folder can be either inside typo3/sysext/ or typo3conf/ext/.

The extension must be programmed so that it does automatically detect where it is located and can work from all two locations.

Local extensions

Local extensions are located in the typo3conf/ext/ directory.

This is where to put extensions which are local for a particular TYPO3 installation. The typo3conf directory is always local, containing local configuration (e.g. LocalConfiguration.php), local modules etc. If you put an extension here it will be available for a single TYPO3 installation only. This is a "per-database" way to install an extension.

System extensions

System extensions are located in the typo3/sysext/ directory.

This is system default extensions which cannot and should not be updated by the EM. They are distributed with TYPO3 core source code and generally understood to be a part of the core system.

Loading precedence

Local extensions take precedence which means that if an extension exists both in typo3conf/ext/ and typo3/sysext/ the one in typo3conf/ext/ is loaded. This means that extensions are loaded in the order of priority local-system.