I have updated a copy of my site from J2.5 to J3.4 on localhost, carefully checking, updating and/or replacing all components, modules, and plugins as needed, and the updated site works fine on localhost. I then use Akeeba to take a backup of the localhost site, copied it up to the live site server and restored it. Now I get error 500 - JHtmlBehavior: :mootools not supported. when I try to access the live site front end, and a white screen when I try to access the back end. How do I proceed from here?

1 Answer 1


JHTML::_('behavior.mootools'); is the code you will need to look for. This was used up until Joomla 3.x, where is was changed.

I'd suggest (on your localhost) you do a mass find with your text editor for the above code and once found, replace it with:

  • I found one instance of that string in a plugin that claimed to be J3.4 compatible, changed it as you suggested, and it worked - many thanks. Why didn't the error show up in the localhost installation?
    – SteveM
    Apr 16, 2015 at 15:58
  • You most likely had error reporting disabled on your localhost which is why the error wasn't showing there. Glad this helped. Please accept the answer by clicking the "tick" icon on the left hand side
    – Lodder
    Apr 16, 2015 at 16:05

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