Pairs almost always with its opposite
线下 xiànxià 'offline / brick-and-mortar.' Compare with
网上 wǎngshàng (also 'online,' more colloquial).
在线 zàixiàn means 'currently online / connected' (a state), whereas
线上 modifies a noun:
线上课程 'online course,'
线上会议 'online meeting.'
