6.000 Extensions and Counting
TYPO3 is an extremely modular system that can be easily enhanced with custom extensions. All TYPO3 sites are built on top of the TYPO3 core, which contains the systems' fundamental functionality. Custom extensions interact with the core through the stable, clearly documented extension API. While the TYPO3 core does change in each new release, the interfaces between extensions and the core do not, ensuring easy updates and future-proof development.
The TYPO3 Extension Manager
TYPO3 relies on the TYPO3 extension manager - included in the TYPO3 core - for installing, activating, and deactivating extensions on a given TYPO3 installation. Extensions can be quickly imported and installed with just a couple clicks in the TYPO3 Admin Interface.