有空吗？

Use it exactly like you would use 'Are you free?' in English. You can drop it into a text message or say it in person. If you want to be specific, add a time before it. For example, 今天有空吗？ (Free today?). It is a 'yes/no' question. People will usually answer with 有空 (I'm free) or 没空 (I'm busy/not free).

Use it when you want to grab coffee with a friend. Use it at work when you need to ask a colleague a quick question. It is perfect for checking if someone is available before you launch into a long story. It is the polite 'knock' on the door of someone's attention. Even at a restaurant, you might ask a waiter 你有空吗 if they look slammed but you need a napkin.

Don't use this if you are talking to someone very high-ranking, like a CEO or a government official. In those cases, it might feel a bit too casual. Also, avoid using it if you are about to ask for a massive, life-changing favor. It sounds a bit too 'light' for that. If you are in a super formal ceremony, stick to more professional openings. Otherwise, it is hard to go wrong.

In Chinese culture, being 'busy' is often seen as a sign of importance. However, asking 有空吗 shows you respect the other person's time. It is a soft way to enter a conversation. In older times, people might have asked about food, but in modern, fast-paced cities like Shanghai or Beijing, time is the new currency. Asking if someone has 'empty time' is a very modern necessity.

If you want to sound more northern (like in Beijing), you might add an 'r' sound: 有空儿吗？ (yǒu kòngr ma). If you are in a rush, you can just say 有空没？ (yǒu kòng méi?). For a slightly more polite version, you can use 您有空吗？ (nín yǒu kòng ma). If you want to be very casual with best friends, just a quick 在干嘛？有空吗？ (What's up? Free?) works wonders.