Welcome to the official TYPO3 API Documentation
TYPO3 source code is well documented and allows you to understand many internals just by browsing through the various classes and methods.
TYPO3 14-dev (main) API
Automatically generated API from the 14-dev (main) branch of TYPO3.
TYPO3 13.4 API
Automatically generated API from the 13.4 (current stable) branch of TYPO3.
TYPO3 12.4 API
Automatically generated API from the 12.4 (old stable) branch of TYPO3.