Project Structure and Autoloading in Bitrix

Baseline: main 23.0+. Features newer than baseline are marked Since.

Three Root Sections

• /bitrix/ — system files. Never edit them directly: any hotfix will be lost during an update.
• /local/ — all user code. If a file doesn't exist — create it manually. With the same path, a file in /local/ takes precedence over /bitrix/.
• /upload/ — files uploaded by users and modules.

What to Put in /local/