There is a much simpler way. Log in to the Manager.
MODX Revolution
2.2.x and earlier: go to System -> Content Types .
2.3.x and later: go to Content -> Content Types .
Find HTML and erase what is written in "File Extension". You do this by double-clicking .html in the table to activate the editable field. After deleting the contents, clear the cache.
MODX Evolution
Go to Tools -> Configuration -> Friendly URLs .
Delete content in the "Friendly Suffix URL". Save and clear the cache.
Optimuscrime
source share