Welcome to the official TYPO3 Documentation 

TYPO3 CMS is an Open Source Enterprise Content Management System powered by PHP.

Getting started guide 

This guide introduces some of the core concepts of TYPO3, guides you through installation, helps you set up your first small project with a custom template, and gives you information on troubleshooting.

Site package tutorial 

This tutorial describes step by step how to create your first site package or theme in TYPO3 from scratch.

Editors guide 

Learn about how you log into the TYPO3 backend, how to work with the page tree, how to create and manage content, how to work with translations and other useful tricks for editors.

Download TYPO3 

For information about the different versions of TYPO3 and their system requirements, visit https://get.typo3.org

You can also download the sources from there. We suggest Installing TYPO3 using Composer, however.

References 

TYPO3 explained
The main document for advanced developers and integrators. It describes the API, coding guidelines, configuration options and security guidelines. Introduces creating an extension to enhance TYPO3.
TYPO3 Core changelog
Learn what is new in TYPO3 and how to migrate away from deprecated functionality.
Fluid Explained
Fluid is a PHP template engine and is the de facto standard for any HTML-based output in the TYPO3 CMS.
Fluid ViewHelper reference
Complete reference of all Fluid ViewHelpers provided by TYPO3. Used to add logic and functionality to your templates.
TypoScript Explained (including TSconfig)
Complete reference of TypoScript settings and configuration options. Frontend TypoScript is useful to improve the frontend output of your site, while TSconfig options let you customize the TYPO3 backend.
TCA reference
Complete reference of the Table Configuration Array (TCA) which maps raw database tables to records in the TYPO3 backend and in Extbase.