WordPress Version Upgrade Guide: A Step-by-Step Manual

1. Why Regular WordPress Upgrades Matter

WordPress releases minor updates approximately every month and major version updates (e.g., 6.4 → 6.5) roughly every three months. Keeping your installation current is critical for three reasons:

• Security: Most critical patches address vulnerabilities that malicious actors actively exploit. Running outdated core files is the #1 reason sites get compromised.
• Compatibility: Modern PHP versions and hosting environments require updated core files to function optimally and avoid deprecation notices.
• Performance: Each release includes database optimizations, loading improvements, and deprecated code removal that directly impact page speed scores.

2. Pre-Upgrade Checklist

Before touching the upgrade button, verify the following conditions are met:

1. PHP Version: Ensure your server runs PHP 7.4 or higher (PHP 8.0+ recommended for WP 6.4+).
2. MySQL/MariaDB: Minimum version 5.7 or MariaDB 10.4.
3. Active Theme: Must be compatible with the target WordPress version.
4. Plugin Compatibility: Check author notes or test on a staging site first.
5. Disable Aggressive Caching: Temporarily turn off server-level or plugin caching to prevent stale content after upgrade.

3. How to Backup Your Site Safely

Even with a flawless process, upgrades can fail. A complete backup is non-negotiable. A proper backup includes:

• WordPress Core Files (excluding /wp-content/)
• wp-content/ directory (themes, plugins, uploads, mu-plugins)
• Database dump (all tables, including wp_options and custom tables)

Recommended Methods:

• Plugin-based: UpdraftPlus, Duplicator, or BlogVault
• Hosting Panel: cPanel/Cloudways/Plesk native backup tools
• Command Line:

  mysqldump -u [username] -p [database_name] > wp_backup_$(date +%F).sql
  tar -czf wp_files_$(date +%F).tar.gz /path/to/wordpress/

4. Update Themes & Plugins First

Always update dependencies before the core. Outdated plugins are the primary cause of upgrade failures and fatal PHP errors.

1. Navigate to Dashboard → Plugins → Installed Plugins
2. Review each plugin's compatibility status and developer notes
3. Deactivate unnecessary or abandoned plugins temporarily
4. Update remaining plugins one by one (not in bulk, to isolate conflicts)
5. Repeat for Appearance → Themes

If you run a high-traffic site, clone your production environment to staging, perform the full upgrade sequence there, and verify functionality before touching the live site.

5. Performing the Core Upgrade

Once prerequisites are met, initiate the upgrade:

1. Log in to /wp-admin
2. If a banner appears, click Now update to WordPress X.X
3. If no banner exists, go to Dashboard → Updates
4. Click Update Now and wait for the process to complete
5. Log back in (authentication may be required post-upgrade)

Alternative: CLI Upgrade (Recommended for Developers)

wp core update --force
wp core verify-checksums
wp cache flush

The WP-CLI method is faster, more reliable, and avoids PHP memory limit issues that sometimes occur with the GUI updater on resource-constrained hosts.

6. Post-Upgrade Verification

After the core updates, run through this verification checklist:

• ✅ Frontend loads correctly across devices
• ✅ Admin dashboard loads without PHP errors
• ✅ Permalinks are functioning (Settings → Permalinks → Save Changes if broken)
• ✅ Forms, checkout flows, and contact methods work
• ✅ Analytics and tracking scripts are firing
• ✅ No console errors or mixed content warnings
• ✅ Run a security scan (Wordfence, Sucuri, or Wp Admin automated check)

Re-enable any caching layers you disabled earlier and purge the CDN cache.

7. Troubleshooting Common Upgrade Issues

White Screen of Death (WSOD)

Usually caused by a memory limit or plugin conflict. Increase WP_MEMORY_LIMIT in wp-config.php:

define( 'WP_MEMORY_LIMIT', '256M' );

If that fails, rename the /wp-content/plugins/ folder via FTP/SFTP to force deactivate all plugins, then reactivate one by one.

Broken Permalinks

Navigate to Settings → Permalinks and click Save Changes. This regenerates the .htaccess file (Apache) or Nginx rewrite rules.

Deprecated Function Errors

Check your /wp-content/debug.log file. These are usually plugin/theme related. Contact the developer or replace with an actively maintained alternative.