How to Check WP_DEBUG Logs in WordPress

WP_DEBUG is a WordPress constant that enables debugging mode, allowing developers to troubleshoot issues by logging errors, warnings, and notices. This guide explains how to check WP_DEBUG logs using various methods.

Prerequisites

• Access to your WordPress installation (via hosting control panel, FTP, or SSH).
• Basic understanding of WordPress configuration files.
• WP_DEBUG enabled in your wp-config.php file. To enable it, add or modify the following lines:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false ); // Prevents errors from displaying on the site

Method 1: Checking Debug Logs via File Access

WordPress stores debug logs in a file when WP_DEBUG_LOG is enabled. By default, the log file is located at wp-content/debug.log, but you can specify a custom location for better organization or security.

Steps:

1. Configure Log Location:

• For the default log location, ensure WP_DEBUG_LOG is set to true in wp-config.php.
• For a custom log location, add or edit the following line in wp-config.php to specify a path:

define( 'WP_DEBUG_LOG', '/path/to/custom/debug.log' );

• Ensure the directory is writable by the web server (e.g., set permissions to 664 or 666 for the file and 755 for the directory).

1. Access Your WordPress Files:

• Use an FTP client (e.g., FileZilla) or your hosting file manager to access your WordPress installation.
• Alternatively, use SSH to connect to your server for faster access.

1. Locate the Debug Log:

• Navigate to the wp-content directory for the default log (wp-content/debug.log) or to your custom path (e.g., /path/to/custom/debug.log).
• If the log file doesn’t exist, ensure WP_DEBUG_LOG is correctly configured and trigger an action on your site (e.g., refreshing a page) to generate logs.

1. View the Log:

• Download the log file and open it with a text editor (e.g., Notepad++, VS Code).
• Alternatively, use SSH to view the file directly with a command like cat wp-content/debug.log or cat /path/to/custom/debug.log.

1. Interpret the Logs:

• Logs include timestamps, error types (e.g., PHP Warning, PHP Notice), and details about the issue, including the file and line number causing the error.

Notes:

• Custom log locations are useful when wp-content is not writable or for organizing logs in a secure directory.
• Ensure custom paths are not publicly accessible to prevent exposing sensitive information.
• If the log file is large, use tools like grep (e.g., grep "PHP Error" wp-content/debug.log) to filter specific errors.
• Regularly clear or rotate the log file to prevent it from growing too large.

Method 2: Using a Debugging Plugin

Several WordPress plugins simplify the process of viewing debug logs without direct file access.

Recommended Plugins:

• Debug Log Manager: A dedicated plugin for enabling, managing and viewing debug logs.
• Query Monitor: Displays debug information, including errors, directly in the WordPress admin panel.
• Debug Bar: Adds a debug menu to the admin bar, showing logs and other debugging data.

Steps:

1. Install a Plugin:

• Go to Plugins > Add New in your WordPress admin panel.
• Search for and install your chosen debugging plugin (e.g., Debug Log Manager).
• Activate the plugin.

1. Access Debug Logs:

• For Debug Log Manager, navigate to Tools > Debug Log Manager in the WordPress admin panel to view, filter, or download the debug log. The plugin also allows you to clear logs or configure log settings.
• For Query Monitor, navigate to the Query Monitor menu in the admin bar to view errors and logs.
• For Debug Bar, click the Debug Bar in the admin bar and explore the log section.

Notes:

• Plugins may require WP_DEBUG and WP_DEBUG_LOG to be enabled.
• Debug Log Manager offers additional features like log filtering by error type and log file size management.

Method 3: Real-Time Debugging with a Terminal

For advanced users, you can monitor debug logs in real-time using SSH and terminal commands.

Steps:

1. Access Your Server via SSH:

• Connect to your server using an SSH client (e.g., PuTTY or terminal).

1. Monitor the Debug Log:

• Run the following command to watch the log file in real-time:

tail -f wp-content/debug.log

• For a custom log location, use:

tail -f /path/to/custom/debug.log

• The -f flag ensures new log entries are displayed as they are written.

1. Trigger Actions:

• Perform actions on your WordPress site (e.g., refresh a page, submit a form) to generate log entries.
• Observe the terminal for immediate feedback.

Notes:

• Use Ctrl+C to stop monitoring.
• Combine with grep for filtering (e.g., tail -f wp-content/debug.log | grep "PHP Error").

Method 4: Using Error Log Integrations

Some hosting providers or server setups allow you to integrate WordPress debug logs with server error logs or third-party monitoring tools.

Steps:

1. Check Hosting Control Panel:

• Log in to your hosting control panel.
• Look for an Error Logs or Logs section.
• If WP_DEBUG_LOG is configured to write to a server-accessible file, errors may appear here.

1. Integrate with Third-Party Tools:

• Use tools like New Relic, Sentry, or Loggly to collect and analyze WordPress debug logs.
• Configure these tools via plugins or by directing WP_DEBUG_LOG output to their APIs.

Notes:

• This method requires additional setup and may involve costs for third-party services.
• Ensure your hosting environment supports custom log integrations.

Best Practices

• Disable Debugging on Live Sites: Set WP_DEBUG to false on production sites to prevent exposing sensitive information.
• Secure Log Files: Ensure debug.log is not publicly accessible (e.g., add deny from all to .htaccess for the log file).
• Regular Maintenance: Periodically clear or archive logs to manage disk space.
• Test in Staging: Replicate issues in a staging environment to avoid disrupting live sites.

Troubleshooting Common Issues

No debug.log File:

• Verify WP_DEBUG and WP_DEBUG_LOG are set to true in wp-config.php.
• Check if the wp-content directory or custom log directory is writable (permissions should be 755 for directories and 664 or 666 for files).

Logs Are Empty:

• Ensure actions triggering errors are performed after enabling debugging.
• Check for syntax errors in wp-config.php that might prevent logging.

Large Log Files:

• Use log rotation tools or plugins like Debug Log Manager to manage file size.
• Filter logs with tools like grep to focus on relevant entries.

By using these methods, you can effectively monitor and troubleshoot issues in your WordPress site using WP_DEBUG logs. Choose the method that best fits your technical expertise and hosting environment.