Configuration of custom URL extensions (.html or other)

The procedure is the same for extension-less URLs. You will only configure a different extension at the end of the procedure:

Go to Site Manager -> Settings -> select Global or particular web site -> URLs -> set Friendly URL Extension value to .html and click Save.

Now when you go to the live web site, you will see that all URLs in menus and listings are rendered with .html extension. You may, however, need to update some static links that were created with default .aspx extension.