Upgrading from Joomla 3.10 to Joomla 4: A Practical, Low‑Risk Checklist When Extensions Block the Update

Quick reality check: risks and expected outcomes

Joomla 4 is a major upgrade with modernised code and APIs. That means third‑party extensions and template overrides that were written for Joomla 3 can cause most of the problems during migration. A methodical approach dramatically reduces the chance of a broken production site.

What typically breaks during this upgrade

• PHP fatal errors caused by incompatible extension code.
• Layout or styling issues from template overrides that rely on Joomla 3 APIs.
• Broken third‑party integrations (payment gateways, SSO, external APIs) due to API changes or deprecated functions.

When it’s usually safe to proceed

• All critical extensions and the active template are confirmed compatible with Joomla 4, or non‑critical items can be disabled or replaced.
• You have a functioning staging upgrade and a tested rollback plan.
• You have recent full backups (files + database) stored off the server.

Practical examples:

• Scenario A: A simple brochure site using only core articles and a modern template — low risk after a staging test.
• Scenario B: A site with multiple custom components and an old, heavily‑overridden template — higher risk and likely requires developer help.

Step 1 — Inventory your site (extensions, templates, custom code)

Before changing anything, create a simple inventory so you know what must be checked for compatibility.

How to list installed extensions and plugins (Administrator tools)

1. Open Administrator → Extensions → Manage → Manage to see installed extensions and versions. Record each item: name, type (component/module/plugin), version, and vendor.
2. Check Administrator → Extensions → Manage → Database and Discover for orphaned or hidden items.
3. Create a spreadsheet with columns: Name | Type | Version | Vendor | Purpose | Critical? | Compatibility status.

Where to find template overrides and custom code

• Template overrides are stored in /templates/your_template/html — list the components that have overrides.
• Look for custom folders in /components, /modules, /plugins, /libraries or nonstandard files in /media.
• Note any patched core files or developer folders; custom code often requires developer attention to port to Joomla 4.

How to prioritise extensions (critical vs optional)

• Critical: login, user management, eCommerce, payments, booking, membership systems.
• Optional: analytics modules, social widgets, aesthetic modules that can be disabled temporarily.

Starter checklist (copy & paste):

1. Export or manually record Extensions → Manage list.
2. Note the active template under Extensions → Templates → Styles.
3. List template overrides in /templates/your_template/html.
4. Mark each extension as Critical or Optional.
5. Save the spreadsheet and attach it to your backup files.

Step 2 — Back up and create a staging site

Never attempt a major core upgrade on production without a tested full backup and a separate staging environment that mirrors production.

Recommended backup tools and strategies

• Use a reliable Joomla backup tool (Akeeba Backup is commonly used) or your host’s snapshot feature. Keep copies off the same server.
• Download a copy of the backup to local or cloud storage as an extra precaution.
• Test the restore process on a staging server before performing live upgrades.

Creating a staging copy using backup/restore tools

1. Option A: Create a full archive on live with your backup extension, then restore to a subdomain (a protected staging subdomain) using the backup tool’s restore scripts.
2. Option B: Use a host-provided cloning/staging feature (often faster and safer).
3. Update configuration.php on staging with the staging database credentials and secure the staging site (password‑protect or disallow indexing).

Testing the staging site before upgrade

• Verify front‑end pages, admin login, and all critical extensions behave like production.
• Record any preexisting errors or warnings so you can separate them from upgrade regressions.

Step 3 — Check server and PHP requirements

Joomla 4 requires newer PHP and certain PHP extensions. Confirm exact requirements from official Joomla documentation and make the staging environment match the target production environment.

Joomla 4 system requirements — what to check

• Confirm minimum and recommended PHP versions, the list of required PHP extensions (for example: mbstring, json, and MySQLi or equivalent), and supported database versions.
• Check file permissions and PHP ini settings: memory_limit, max_execution_time, and upload_max_filesize.
• Ensure your hosting allows switching PHP versions per site/account before attempting changes on production.

How to change PHP version on common hosts

• Many control panels (cPanel, Plesk) provide a PHP selector — change PHP on staging first and monitor logs after the switch.
• If your host needs a support ticket to change PHP, schedule during low-traffic windows.

Recommended PHP settings to test on staging

• Increase memory_limit if you have many extensions (for example, 256M+), and increase max_execution_time during upgrade operations.
• Enable all PHP extensions required by Joomla and by your extensions.
• Monitor error logs when switching PHP versions to spot deprecation notices early.

Step 4 — Audit extensions and plan fixes or replacements

Identify which extensions are Joomla 4 compatible and make a decision for each: update, replace, disable, or port.

Where to find extension compatibility info (JED, vendor pages)

• Check the Joomla Extensions Directory (JED) listings and the vendor’s website or GitHub repository for compatibility notes and release roadmaps.
• If information is missing, mark the extension as 'unknown' and test carefully on staging or contact the vendor for clarification.

Disabling vs uninstalling: safe practices before upgrade

• Temporarily disable non‑essential extensions on staging to confirm whether they are required; disabling is reversible and safer than uninstalling.
• Uninstall only after confirming the extension is unused and after backing up any related data — many components have dedicated database tables that may be removed on uninstall.

Fixes: update, replace, patch, or remove — decision matrix

• Update: Vendor provides a Joomla 4 compatible release — plan to update on staging first.
• Replace: Find a maintained alternative extension that covers the required functionality.
• Port/Patch: Hire a developer to update the extension to Joomla 4 APIs — typically the most costly option.
• Remove/Workaround: Disable the extension and provide a temporary manual alternative if feasible.

Practical spreadsheet row example:

• Extension X | Component | v2.1 | Vendor | Critical: Yes | Compatibility: Unknown | Action: Test on staging; contact vendor; prepare replacement if no update.

Step 5 — Run pre‑upgrade checks and resolve warnings

Use Joomla’s diagnostic tools on staging to identify blockers and fix them before attempting the core upgrade.

Using Joomla pre‑upgrade check tools and interpreting warnings

• Run the available pre‑update checks on Joomla 3.10 (verify the exact menu location in your installation). Classify each result as Info, Warning, or Critical.
• Document each issue and at least one mitigation or action item for it.

Common warnings and straightforward fixes

• Missing PHP extensions — enable them in your PHP configuration via the hosting control panel.
• Deprecated function notices from third‑party extensions — update or disable the offending extension.
• Template compatibility warnings — test using a default Joomla template that is known to work with Joomla 4 to isolate issues.

Disabling non‑critical plugins before upgrade

• Disable analytics, tracking, or social plugins on staging to reduce complexity during the upgrade process. Re‑enable them one by one after a successful upgrade.

Step 6 — Upgrade process (staging first, then live)

Follow a consistent, documented process. If staging succeeds, repeat the same steps on production during a planned maintenance window.

Step‑by‑step upgrade on staging

1. Confirm staging uses the target PHP version and that pre‑checks are resolved.
2. Update all extensions that already have Joomla 4 compatible versions.
3. Disable or remove incompatible/non‑critical extensions identified in your audit.
4. Run the Joomla core upgrade via the Joomla Update component; watch for any errors.
5. Clear caches, check front end and admin area, and run your functional test list.

Upgrading the live site with minimal downtime

1. Schedule the upgrade during low traffic and notify stakeholders.
2. Put the site in maintenance mode, create and download a final full backup.
3. Repeat the verified staging steps exactly on live: update extensions, disable problematic plugins, run core upgrade.
4. After upgrade, test login, forms, checkout, and key flows before removing maintenance mode.

Logging, monitoring, and immediate checks

• Monitor server error logs and Joomla logs for new errors; enable temporary debugging logs if necessary.
• Check for missing assets, broken module positions, or layout regressions.

Step 7 — Post‑upgrade checklist and testing

After a successful upgrade, follow a structured acceptance test and re‑enable optional extensions gradually.

Functional tests to run immediately

• Front‑end: homepage, navigation, search, key landing pages, forms submissions.
• Admin: login, menu editing, user management, extension updates.
• Transactions: perform a test order, test payment gateways, and confirm emails are sent.

Performance and SEO checks

• Measure page load times and server response—note any regressions from previous baselines.
• Verify that SEF URLs, canonical tags, robots.txt, and sitemap generation behave as before.

Handling template and override issues

• If the template causes layout problems, try switching temporarily to a Joomla 4 compatible default template to determine whether the template or core is the cause.
• Review and update template overrides in /templates/your_template/html to match the new component view structure.

Troubleshooting common problems and rollbacks

If something goes wrong, gather evidence and restore from backup if required. Work methodically to avoid losing newer content.

If the upgrade fails: restoring from backup

• Use your backup tool’s restore process (for example, Akeeba Kickstart) or the host snapshot rollback to restore files and database.
• If possible, test the restore on a staging server before modifying live production again.
• Document the failure, include timestamps, and collect logs for post‑mortem analysis.

Collecting logs and error information

• Collect server error logs (Apache/nginx/PHP), Joomla logs from the /logs directory, and any stack traces or browser console errors.
• Note the URL visited, exact error message, and time of occurrence—this helps correlate with server logs.

Common specific problems and first steps

• White screen / 500 error: check the server error log for fatal PHP errors; consider temporarily enabling PHP error display on staging only.
• Missing CSS/JS: clear Joomla and browser caches, confirm static assets were migrated and file permissions are correct.
• Extension fatal error: if the admin is inaccessible, disable the extension in the database (only if you are comfortable with SQL and after backing up the DB).

When to hire a developer — handing off a clear brief

Hire a Joomla developer when a critical extension is abandoned, when you have heavy custom code, or when template porting is required. Provide a clear brief to get accurate estimates and faster work.

What information to include in a contractor brief

• Site URL and current versions (Joomla 3.10, current PHP version).
• Access details: create a temporary admin account and provide staging SFTP or hosting control panel access (with expiry).
• Backup location and latest backup timestamp.
• Spreadsheet of installed extensions with critical flags and compatibility notes.
• List of critical features that must remain functional after the upgrade (checkout, login, forms).

Choosing a Joomla specialist

• Prefer developers with published Joomla 4 migration experience and references.
• Ask for a written plan, the estimated timeline, testing checklist, and a rollback strategy.

Security and credential best practices

• Provide temporary, revocable credentials and use secure channels for sharing them.
• Prefer that work occurs on staging rather than directly on live site when possible.

Sample contractor brief (copyable):

• Site: https://your production domain
• Current Joomla: 3.10.x; Current PHP: 7.4 (note: target PHP version will be provided)
• Admin user: please create temporary username 'contractor_test' with Super User for 7 days
• Backup: Latest Akeeba archive stored at /backups/backup-2026-05-10.zip
• Problem extensions: component X (critical — no Joomla 4 release), module Y (optional)
• Desired outcome: Successful upgrade to Joomla 4 with checkout and login working; provide estimate to port component X or recommend a replacement.

FAQ

Will my site "blow up" if I try the Joomla 4 update?

Not necessarily. Risk depends on the number and importance of incompatible extensions and template overrides. A safe path is to inventory extensions, create and test a staging copy, run pre‑update checks, and upgrade live only after a successful staging upgrade and backups. If you are unsure, consult a Joomla developer.

How can I tell which extensions are incompatible with Joomla 4?

Check the Extension Manager, the Joomla Extensions Directory (JED), and vendor release notes for compatibility information. Run Joomla’s pre‑upgrade checks on staging to surface warnings that point to specific extensions.

Do I need to change my PHP version before upgrading?

Joomla 4 requires newer PHP than Joomla 3.10. Test the recommended PHP version for Joomla 4 on staging first and plan the live PHP change carefully. Verify exact PHP version requirements against the official Joomla documentation before making production changes.

What if a critical extension has no Joomla 4 update?

Options include: postponing the upgrade and keeping the extension active; replacing the extension with a maintained alternative; or hiring a developer to port the extension. Evaluate cost, security risk, and business impact before choosing.

How do I roll back if the upgrade breaks the site?

Restore a recent full backup (files + database) using your backup tool or host snapshot. Document the failure, collect logs for investigation, and reattempt the upgrade on staging after addressing the cause.

Can I upgrade automatically, or must I update/replace extensions first?

Best practice is to update compatible extensions first and resolve or disable incompatible ones on staging before running the core upgrade. Upgrading automatically without addressing incompatibilities increases the risk of failure.

How long should I monitor the site after upgrading?

Monitor logs and key user flows for at least 24–72 hours; longer monitoring is recommended for transactional or high‑traffic sites. Re‑enable disabled plugins gradually and track any regressions.

Conclusion

Upgrading from Joomla 3.10 to Joomla 4 is achievable with a careful, repeatable process: inventory your site, back up and create staging, verify server/PHP requirements, audit extensions and plan replacements or fixes, run pre‑upgrade checks, perform the upgrade on staging first, and then upgrade the live site using the same verified steps. When facing custom or abandoned extensions, prepare a clear brief and hire a Joomla developer. Always verify version and requirement details against the official Joomla documentation before making production changes.

Further reading and next steps

• Prepare your inventory spreadsheet and attach it to the backup before cloning to staging.
• Test PHP version switches on staging and review error logs.
• If you need help, gather the logs and the spreadsheet created in Step 1 before contacting a developer.