The BBC's iPlayer catch-up service will require users to enter a password to access it within the next few weeks.
The move was announced last year, but will soon come into force.
The BBC has denied this is to help it find who is watching without a TV licence, though it added that registering email addresses linked to accounts will help it to identify who has and hasn't paid up.
If you fire up iPlayer, you'll now see a message saying you'll "soon need to sign in to watch". You'll be encouraged to do so before the deadline in a few weeks.
According to Andrew Scott, launch director of MyBBC, the move is intended to make the BBC's services "more personal and relevant to you."
"Signing in allows you to receive recommendations for programmes you might like," he wrote in a blog post announcing the move. "You can receive alerts about world events, hot topics and things you've told us you're interested in. You can also get other benefits like starting to watch a programme on one device and picking up where you left off on another."