References

Reference manuals are exhaustive documents about one particular aspect of TYPO3 CMS: important APIs, TypoScript options, TCA properties, etc.

If you are new to TYPO3 CMS and feel lost in such documents, please make sure that you have been through all the available tutorials.

Manual Description
Core ChangeLog New Features, Breaking Changes, Deprecations. Reading up here is strongly recommended for developers. For everyone else, the What's new slides provide the information in a more digestible way.
Core API A technical reference of the TYPO3 core. Reading this is strongly recommended for core developers and extension developers. Also contains Coding Guidelines.
TCA Reference Reference for the Table Configuration Array (TCA). TCA can be used to extend the definition of database tables.
TSconfig Reference Reference to Page TSconfig and User TSconfig. This is used to configurate the backend.
TypoScript Reference TypoScript is a configuration language that is specific to TYPO3. This is used to configure the frontend. For an introduction see the TypoScript in 45 Minutes tutorial.

With our ongoing consolidation efforts, some documents have been merged into other documents for better overview, less duplication and confusion. The latest versions of these documents only show a "Has been moved" message, but in case outdated information for older TYPO3 versions is looked for, these obsoleted documents are listed here:

Manual Description
(OLD) Inside TYPO3 OLD, current core v9 version has been integrated into Core API
(OLD) Core Coding Guidelines OLD, current core v9 version has been integrated into Core API
(OLD) TypoScript Syntax and In-depth Study OLD, current core v9 version has been integrated into Core API
(OLD) Services API OLD, current core v9 version has been integrated into Core API
(OLD) File Abstraction Layer OLD, current core v9 version has been integrated into Core API