Alex King

Crowd Favorite

If you’ve decided to move things around on your site, you might overlook a few redirects and end up with some broken URLs. This will help you catch those so you can take care of them.

404 Notifier

Log 404 (file not found) errors on your site and get them delivered to you via e-mail or RSS.

Andrew Klimek

If the log is long, the latest lines are show at the top to avoid scrolling. Line numbers are shown for reference.
Logs over 5MB do not load until you confirm you are sure, or you can opt to delete the log and start afresh.
Only admins can view (or anyone you give the capability “manage_options”).
Debug Log only works if it’s enabled in wp-config.php. See https://codex.wordpress.org/Debugging_in_WordPress#WP_DEBUG_LOG
Recommended configuration:
<pre><code>define( 'WP_DEBUG', true );// just toggle this line to false to turn off
if ( WP_DEBUG ) {
 define( 'WP_DEBUG_LOG', true );
 define( 'WP_DEBUG_DISPLAY', false );
 @ini_set( 'display_errors', 0 );
}
</code></pre>

Debug Log

View and Delete the debug log from the Tools menu.  Extremely light and simple.

404 Notifier vs Debug Log