How to Actually Pay for a Ride
Beijing's subway is cash-unfriendly in practice, even though ticket machines technically accept cash — the real default for both locals and increasingly for tourists is a QR code payment through Alipay or WeChat Pay, tapped at turnstile scanners on entry and exit. Setting up Alipay's 'Tour Pass' feature (which lets foreign credit cards load a usable in-app wallet without a Chinese bank account) before you land is the single most useful piece of prep for getting around Beijing smoothly, not just for the subway but for virtually everything else cash-based in the city.
The alternative is a physical Yikatong transit card, sold and topped up at station service counters and some convenience stores, which also works on buses and some taxis. It requires a cash or card deposit, refundable when you return the card before leaving — useful if you'd rather not set up a Chinese payment app at all.

