How to Update Joomla Template Overrides After a Joomla Upgrade
Review override notifications after the upgrade
After Joomla finishes updating, open System → Templates → Site Templates and inspect the relevant template in Templates: Customise. Joomla's Updated Files tab can list overrides whose upstream source changed during a Joomla or extension update. Treat each entry as a review task, not an automatic instruction to replace your file.
Back up before merging changes
Take a current backup and preserve the existing override before editing. If possible, perform the comparison and testing on staging. The live override may contain deliberate customizations, so replacing it with the new core file without review can remove site-specific behavior just as surely as ignoring upstream changes can preserve obsolete code.
Compare the override with the new source file
Use Joomla's available comparison information or a dedicated diff tool to compare the override with the current upstream layout. Identify both sets of changes: what your site customized and what Joomla changed. Pay particular attention to security-related escaping, accessibility markup, data attributes, helper calls, and changed variables.
Reapply only the customization that is still required
Start from the current upstream layout when the differences are substantial, then reintroduce the site's necessary modifications. For a small override, a careful merge may be sufficient. Avoid copying old upstream code forward merely to preserve a few custom lines.
Test every view that uses the override
Verify the exact frontend or Administrator routes affected by the file. Test responsive behavior, forms, login state, accessibility, JavaScript interactions, and relevant modules or plugins. Review PHP and browser-console errors. A syntactically valid merge can still break behavior expected by the updated Joomla code.
Mark the review complete only after testing
Joomla's override-management tools let administrators mark reviewed override changes as checked. Use that status to represent completed review, not merely awareness of the notification. If several people maintain the site, document who reviewed the override and which Joomla release was tested.
Repeat the process for extension updates too
Override drift is not limited to Joomla core. Component, module, plugin, and layout source files can change when third-party extensions are updated. Keep the Installer - Override functionality enabled where appropriate and include override review in the normal post-update checklist for Joomla and extensions.
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