UK ISPs are to start sending "educational letters" to customers identified as downloading copyright material without paying for it.
It is part of the UK government's attempt to crack down on piracy.
BT, Virgin Media, TalkTalk and Sky have agreed to send the missives, which will be emailed rather than posted.
The controversial move has been years in the planning, and some experts believe it is too late to be an effective deterrent.
BT, Virgin Media and Sky will start sending out letters on 17 January, and TalkTalk's campaign will begin at the end of the month.
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