How to report harassment taking place within Battle.net chat (mobile or desktop)
How to report a player for cheating in Diablo III
Reporting your own behavior won't prevent action.
How to report players in Diablo III.
Information on how to report forum posts
How to report a player who is threatening with harming another person or a place
Reporting an Exploit or Hack
How to report another player that is using an offensive or inappropriate BattleTag
Information regarding harassment for streamers
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