The migration from Joomla 3 to Joomla 4 can be quite complicated, depending on the installed plugins, components and settings within. The result can be Error 500, and you cannot access the administrator backend anymore. For free advice on the migration see the end of this article.

We migrated the majority of our clients from Joomla3 to Joomla4 last month, many with different components like Acymailing, RS Forms, Akeeba, Seblod, RO Payments, Email authentication plugin by Michael Ritchey and ofcourse our Component My Member Software. Some of the plugins in your installation might have been abandoned; and are not Joomla4 compatible.

Based on our experience we created a step-by-step list, which generally works well:

1. Create a full backup, for example with Akeebabackup
2. Extensions -> Manage -> Update sites : Rebuild
3. Update all components, also JCE editor
4. Select frontend template Protostar and backend Isis
5. Extensions -> Manage -> Filter for templates. Uninstall all templates except for protostar and isis. If this is the last style, remove at least template related system plugins such as system/plugins/rsmelia).
6. Uninstall plugin “mms export”, “AkeebaStrapper”
7. Extensies -> Manage ->Database : Check for errors in
8. Install latest version MMS 8.0.9_J3
9. Acymailing check configuratie, disable “AcyMailing : (auto)Subscribe during Joomla registration”
10. Create a full backup, for example with Akeebabackup
11. Components -> Joomla update options (Next Joomla) : migrate to Joomla 4
12. Update all components (don't forget MMS 8.1.21_J4), and check if NL language and weblinks are updated
13. Select Cassiopia style as default and choose positions for the enabled modules
14. Delete files from folder /tmp with FTP

Free advice from our team

If you are about to do the migration and don't feel comfortable even with the above step-by-step list, you can fill in our contact form and ask for a free consult based on your configuration. We will host an interactive session and will look at your Joomla 3 backend. At the end we will give you 1 free tip on how to have a smooth migration from J3 to J4.