There is a setting to control whispers on the PC and NPC sheets. Hover over the sheet, on the top right corner, just above the attacks, a "cog" will appear. Click that cog. Scroll down and you will see the setting for whispers. The settings can be set to never whisper, query whisper, whisper toggle, or always whisper. When you are done with the setting click the cog again. If you want to set ALL characters to one type of whisper you can do this: Go to Roll20.net Click the name of your game (not Launch) Click on Settings Click on Game Settings Scroll down to nearly the bottom, change the whisper setting to the desired setting. Save Enter the game in the normal fashion (click Launch) Click the My Settings tab (top right corner) Scroll to the bottom, click Miscellaneous Click Apply Default Settings Find the proper setting, checkmark it. Click Apply and WAIT for the nearly invisible bar to complete. Next, go back through any characters (such as player characters) that should have a different setting and adjust those manually.
