How to Upgrade from Joomla 3.10 to Joomla 4 — A Beginner’s Safe-Upgrade Checklist

Quick overview: What upgrading from Joomla 3.10 to Joomla 4 means

At a high level, the Joomla 4 upgrade is a core CMS migration. The core upgrade itself is supported by the project, but it introduces modern PHP practices and structural changes that can affect how extensions and templates interact with the CMS.

What changes between Joomla 3.10 and Joomla 4 (high level)

• User-facing updates: refreshed admin UI and some frontend improvements.
• Developer-facing updates: modernized code, different API behaviors and stricter PHP usage which can surface incompatibilities in older extensions or template overrides.
• Compatibility risk: the most common causes of failures are third-party extensions, outdated templates, and custom code that rely on deprecated Joomla 3 APIs.

Practical example: if you run a site with a custom template and a dozen third-party extensions, expect to audit and test each extension and the template on staging before upgrading production.

Step 1 — Take a full backup (files + database)

A complete backup is mandatory. A backup without verification is risky — always verify a restore before proceeding.

Recommended backup process

1. Back up site files (all Joomla files, configuration.php, .htaccess, media folders, templates and custom code).
2. Export the database (all tables) using your host's tools or phpMyAdmin.
3. Download copies of both file archive and SQL export and store them offsite (local machine, cloud storage or another server).
4. Verify the backup by restoring to a test location (a subdomain, subfolder or local environment) and confirm the site loads and admin access works.

Recommended tools include established Joomla backup extensions and host backup systems. If you choose an extension, verify the restore procedure in the vendor documentation.

Step 2 — Create a staging/testing copy of your site

Use a staging environment to run the full upgrade and tests. There are three common options: a subdomain on your host (recommended), a subfolder or a local environment.

How to create a staging site: options

1. Subdomain (recommended): copy files and import database to a subdomain such as a protected staging subdomain; update configuration.php with the staging DB credentials and set the live site URL to the staging URL.
2. Local environment: use a local web server stack to host a restored copy for offline testing.
3. Host-provided staging tools: many hosts offer cloning or one-click staging; follow the host documentation.

After cloning, take these steps on staging:

• Disable scheduled jobs and background tasks.
• Disable or prevent outgoing email (or configure a dummy mailer) so you don't send test emails to real users.
• Prevent search engine indexing (robots meta noindex and/or HTTP auth).

Staging should match the target production environment as closely as possible, including the PHP version you plan to run with Joomla 4.

Step 3 — Audit installed extensions, templates and plugins

Create a complete inventory of third‑party code and customizations. This audit lets you plan which items need updates, replacements or removal.

How to export a list of installed extensions

• Manual method: open Administrator > Extensions > Manage and record extension names, types, versions and vendors into a spreadsheet.
• Automated method: some tools or extensions can export the list; alternatively export the database table that records installed extensions — verify SQL methods before running on production.
• Document template overrides separately: list files in /templates/your-template/html and any custom template code.

Where to check extension compatibility

• Check the Joomla Extension Directory (JED) listing for compatibility notes.
• Check vendor websites and GitHub repositories for release notes and issue trackers.
• If compatibility is unclear, contact the vendor, or plan to test the extension in staging and consider replacements for critical functionality.

Practical audit spreadsheet columns: Extension name, Type, Version, Vendor, JED link, Joomla 4 compatible? (Yes/No/Unknown), Action required.

Step 4 — Check PHP and server requirements for Joomla 4

Joomla 4 requires a newer PHP version and may need specific database or web server features. Confirm exact requirements in the official Joomla system requirements before changing anything.

How to update PHP on staging without touching production

• Use your hosting control panel to change the PHP version for the staging subdomain only.
• If the host cannot change PHP per-directory, create a separate staging server or ask your host for a temporary test environment.
• After switching PHP, enable error logging and scan for warnings or fatal errors.

Practical example: set the staging site to the recommended Joomla 4 PHP version (verify the target version with official docs), then visit the admin and frontend to watch for immediate errors or deprecation warnings.

Step 5 — Handle incompatible extensions: update, replace, or remove

For each extension you classified as incompatible or unknown, decide one of three actions: update, replace, or remove.

Decision matrix: update, replace, or remove

• Update: if the vendor provides a Joomla 4 version, install it on staging and test immediately.
• Replace: if no update exists but the feature is critical, find an alternative extension that supports Joomla 4 and plan any data migration.
• Remove/disable: if the extension is non-critical, disable or remove it on staging and test site behavior; verify no orphaned functionality remains.

When to contact extension authors and what to provide

If you contact a vendor, include precise details: extension name and version, Joomla and PHP versions, error screenshots or logs, and reproduction steps. That information helps vendors assess compatibility and provide guidance.

Practical example: an e-commerce extension with no Joomla 4 update — options include migrating to a supported cart extension, hiring a developer to port the extension, or postponing the upgrade while applying security measures to continue running Joomla 3.10 safely for a limited time.

Step 6 — Run the core Joomla update on staging

With staging prepared (backup verified, PHP set, incompatible items addressed), run the core update on the staging site first. Use the Joomla Update component in the Administrator to perform the upgrade and follow any guidance provided there.

Step-by-step: using Joomla Update component safely on staging

1. Confirm you have a verified staging backup.
2. Open Administrator > Components > Joomla Update and review the notes.
3. Start the update and monitor for errors or warnings. Record any messages for troubleshooting.
4. After the update completes, run database fixes if prompted, clear caches, and test the admin login and several frontend pages.

Step 7 — Test thoroughly (functional, visual, performance, forms)

Testing is the core of a safe upgrade. Create and run a test plan that covers the most important user journeys and admin tasks.

Tests to run after upgrade

• Frontend flows: homepage, navigation, contact forms, search, login/logout, account pages, checkout (if applicable).
• Admin tasks: create/edit articles, media upload, extension configuration screens, backups, and user management.
• Visual checks: template layout, menus, and responsive breakpoints.
• Performance & SEO checks: basic page speed, page titles, meta descriptions, sitemap generation and redirects.
• Logs: review PHP and Joomla logs for new warnings or fatal errors.

Example 10-step test plan for a small business site:

1. Access homepage and a few internal pages.
2. Login to admin and create a test article.
3. Upload an image to media manager and insert into an article.
4. Submit contact form and verify email capture (using test mailer).
5. Test search functionality and menus.
6. Verify template appearance on desktop and mobile.
7. Check sitemap and robots settings.
8. Run a basic speed check.
9. Review logs for errors.
10. Ensure extensions used for payments or integrations perform in sandbox mode.

Step 8 — Prepare a rollback and deployment plan for production

When staging tests pass, prepare for production deployment with a clear rollback strategy and a scheduled maintenance window.

Deployment steps and rollback plan

1. Communicate the maintenance window to stakeholders and users, and pause content updates if necessary.
2. Create final production backups (files + database) immediately before beginning the upgrade.
3. Put the production site into maintenance mode and run the Joomla Update in production or swap in a tested upgraded clone.
4. Quickly validate key pages and admin login after the upgrade.
5. If critical failures occur, execute the rollback: restore files and database from the pre-upgrade backup, verify the site and disable maintenance mode.

Alternate approach: prepare an upgraded clone and swap DNS or a load-balancer to minimize downtime, if your hosting architecture supports it.

Common problems and how to fix them

Here are frequent symptoms and practical troubleshooting steps you can try on staging.

Frequent symptoms and first steps

• White screen / PHP fatal error: enable staging debug, check PHP and Joomla logs, identify the file and extension causing the error and disable it.
• Broken admin menus or missing CSS/JS: clear Joomla and browser caches, check template overrides and asset pipelines.
• Extension errors or database schema mismatch: update the extension on staging or disable the extension and investigate the database tables it uses.

How to monitor logs and error reports

• Enable Joomla debug mode on staging to capture detailed traces, then reproduce the error and view the stack trace.
• Check PHP error logs on the server (path varies by host) and the Joomla logs (logs directory) for timestamps and message details.
• Use the error message file path and line number to trace whether the issue is core code, an extension, or a template override.

Post-upgrade checklist and monitoring

After a successful production upgrade, complete the final housekeeping and monitor the site closely for at least a week.

Post-upgrade tasks and monitoring

• Clear all caches and rebuild menus or search indexes if needed.
• Apply any remaining extension updates and verify scheduled tasks run correctly.
• Re-enable backups and automated monitoring tools.
• Monitor error logs, uptime and user reports for 7–14 days and be ready to act on regressions.
• Verify SEO-critical items: sitemaps, canonical URLs and redirects to avoid SEO impact.

FAQ

Conclusion

Upgrading from Joomla 3.10 to Joomla 4 is achievable with careful preparation: take verified backups, clone the site to staging, audit and handle third-party extensions and templates, use the Joomla Update component on staging first, and prepare a tested rollback plan for production. Work step-by-step, document actions and verify technical details against official Joomla documentation or vendor guidance before making production changes.

If you are not comfortable with any step—especially editing templates, managing the database or handling extension migrations—consider hiring a Joomla developer to assist. Verify key technical facts (PHP requirements and official upgrade steps) against the Joomla project documentation before you proceed.