可以用微信吗？

Just say it while holding up your phone with the WeChat app open. You can say it before you order or right when you get to the register. If the merchant says 可以 (kěyǐ), they will either scan your QR code or point to theirs. It is a very smooth process. Don't worry about perfect tones; the context of holding a phone makes it clear.

Use it everywhere! Use it at high-end malls or tiny street stalls selling grilled squid. Use it when paying a taxi driver or buying a single apple from a fruit stand. It is even used when splitting a bill with friends. If money is changing hands, this phrase is relevant. It saves you from the awkward 'I don't have enough cash' moment.

Avoid using it at international bank branches or government offices that might require official bank transfers. Don't use it if you see a giant 'Alipay Only' sign, though most places take both. Also, don't use it in very formal business negotiations to discuss million-dollar contracts. That requires a bit more than a quick scan!

China skipped the credit card era and went straight from cash to mobile. WeChat Pay (and Alipay) is now the heartbeat of the economy. Even street performers and temples have QR codes now. Not being able to use WeChat in China feels like being a fish out of water. It is more than an app; it is a digital wallet, ID, and social hub.

If you want to be even shorter, just ask 微信吗？ (WeChat?). If you want to be super polite, add 请问 (qǐngwèn) at the beginning: 请问可以用微信吗？. You might also hear people ask 微信支付可以吗？ which specifically adds the word for 'pay.' But for a beginner, the standard version is perfect.