Clash Royale has an optional profanity filter that prevents the use of offensive or vulgar words in Clan chat.
You can switch the filter on or off in the Settings page. Once the filter is turned on, it will use asterisks to star out words that are considered offensive.
Note that the filter does not work in retrospect, so if something offensive has been said when the filter was off, these words will not be starred out once the filter gets switched on.
In some cases, the profanity filter can be a bit too careful and star out innocent phrases. Please bear with us as we work on making it better at spotting only offensive words.