Galactic assault, heroes showdown and heroes vs villians is only online, the rest of big modes can be played offline (instant action, arcade, battle escenarios, a short but good campaign and starfighters arcade), one thing that cannot be enjoyed offline are AT-AT walkers, AT-TE walkers and separatists MTTs as the heavy vehicles atm are Galactic assault exclusive, also keep in mind that the pc version requires being online to play the game, so it's not online, if you plan to buy for xbox or ps4 that's not a problem i think.