Manual:Null revision

A null revision is created when certain actions are performed on pages or their revisions. The null revision has the same as its parent. It causes the log event to be displayed in the page history. These are created by Revision::newNullRevision.

Log events that create null revisions

 * Imports
 * Page moves
 * Page protection, unprotection, or changing protection level

Log events that do not create null revisions

 * Changing visibility of deletions (revision deletion)
 * Merges
 * Page deletions
 * Page restorations
 * Patrol events