How to fix websites that break after migrating to J! 4.x because of “deprecated code”.
A common experienceI couldn’t tell you how often this problem occurs but the issue arises on The Joomla Forum™ about twice a week. that people have after “successfully” updating from J! 3.10 to J! 4.x is that their website breaks. It doesn’t happen all the time—i.e. every time people migrate from J! 3.x to J! 4.x—but it can catch people by surprise. One of the most common reasons why websites will break is because their J! 3.10 site had one or more third-party extensions installed that used “deprecated code”Further information about potential backward compatibility changes J! 4 may be found here: Potential backward compatibility issues in Joomla 4. If you didn’t install any third-party extensions then you can ignore the rest of this topicIf you have not installed any third-party extensions in J! 3.10 then your migration to J! 4.x should proceed successfully but there may be other factors—not involving “deprecated code”—that can complicate the upgrade..
