Here are the most practical ways to check.
1. Use Joomla’s Pre-Update Check
If your site is currently running Joomla 5.4.x, Joomla already gives you a helpful starting point.
Go to System > Update > Joomla, open Options, and set the Update Channel to Joomla Next. After that, review the Extensions tab in the pre-update check.
You will usually see extensions grouped into categories such as:
- No Update Required
- Extensions that may need attention or updates
This is a useful first look, but it is not a perfect answer. The result depends partly on information provided by extension developers, so treat it as guidance, not a final guarantee.
2. Check Whether the Extension Only Works with the Compatibility Plugin
Joomla 6 includes the Behaviour - Backward Compatibility 6 plugin, which helps older Joomla 5 extensions keep working by adding a compatibility layer.
That sounds helpful, but there is an important detail: an extension is only truly natively compatible if it still works properly when this plugin is disabled.
In other words, if the extension only works because the compatibility plugin is rescuing it, then it may not be fully ready for Joomla 6 in the long run.
3. Verify on the Developer’s Website and in JED
Before trusting any extension, check the developer’s official website. Look for clear statements such as:
- Compatible with Joomla 6
- Tested with Joomla 6
- Requires Joomla 6.x
- Latest version supports Joomla 6
You can also look at the Joomla Extensions Directory (JED) for version tags and compatibility icons.
Still, be careful here. JED information is often submitted by developers themselves, so it is a good clue, but not always the full story. If something looks unclear, the developer’s own changelog or support page is usually more reliable.
4. Test on a Staging Site First
This is the step that matters most.
Before updating your live site, create a backup and restore it to a staging environment or subdomain. Then run the Joomla 6 upgrade there first.
After upgrading, test the extension properly:
- Open its settings
- Save changes
- Check the front end
- Test forms, filters, or any key features
- Look for layout or JavaScript issues
If possible, enable System Debug during testing. That can help you spot warnings or errors caused by incompatible extensions.
A staging test tells you far more than any icon or label ever will.
5. Be Ready to Disable a Problem Extension
If an extension breaks your site after upgrade, do not panic.
In some cases, you may need to disable the extension manually in the database through the #__extensions table to restore backend access. This is one more reason why testing on staging is so important before touching the live site.
Final Thoughts
The safest way to check Joomla 6 compatibility is to combine all of these methods.
Start with the Pre-Update Check, review whether the extension depends on the Backward Compatibility plugin, verify the developer’s official support statement, and most importantly, test everything on a staging site.
If an extension passes all of those checks, you can move into Joomla 6 with much more confidence.
