Extbase has been delivered as a system extension since TYPO 4.3.0 and it has been developed in parallel with the former TYPO3 FLOW, which then was a TYPO3 Association sponsored project. The version numbers of Extbase and Fluid match the version number of TYPO3 core since 4.6.0.

Although Extbase is available in TYPO3 since version 4.3.0, we recommend that you use a supported version to get best performance and security.