Upgrade GuideΒΆ

This document outlines changes introduced in different versions of phpBB. These changes may require adjustments to your existing custom PHP code or Extension code when upgrading to specific versions from a prior versions of phpBB. It is mainly meant to be used by core and Extension developers and does not provide end user documentation for upgrading.

Unless explicitly stated otherwise, each version describes the changes compared to the previous major or minor version that directly preceded it. For example the upgrade guide for 4.0 will describe the changes compared to 3.3 whereas an upgrade guide for 4.1 will describe the changes compared to 4.0.