Valve, owner of online PC gaming platform Steam, and five other publishers have been fined a total of 7.8m (£6.9m) for restricting cross-border sales of PC video games.
So-called geo-blocking means games are locked, so that a cheaper licence intended for less well-off European countries cannot be used elsewhere.
That stopped gamers “shopping around” for the best deals, said EU Competition Commissioner Margrethe Vestager.
Valve said that it planned to appeal.
The other publishers fined were: