# 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 both 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.