欢迎光临！

You will mostly hear this rather than say it. Shopkeepers and waiters shout it out when you walk in. If you are hosting a party, you can say it at the door. You don't need to say much back. A simple smile or a small nod is perfect. It sets a friendly tone for the entire interaction.

Use it when you are the 'host' of a space. This applies to your home, your office, or your store. It is perfect for formal events like weddings or business openings. You can also use it in a text if a friend is coming over. It makes people feel special and expected. It is the ultimate 'open door' expression.

Do not use this if you are the guest. That would be like walking into a party and welcoming the host! Also, avoid using it in very somber or sad situations. It is a bright, upbeat greeting. Don't say it to a stranger on the street just passing by. It requires a destination, like a room or a shop.

This phrase reflects the deep-rooted Chinese value of 'Mianzi' or face. By using 光临, you are giving the guest 'light' or honor. Historically, it was very formal. Today, it is the standard 'hello' for the service industry. In some big cities, shops even have electronic sensors that shout it automatically. It is the soundtrack of Chinese commerce!

If you want to be shorter, just say 欢迎. For a very fancy event, you might hear 热烈欢迎. That means 'a warm and enthusiastic welcome.' In casual settings with close friends, you might just say 快进来. That means 'come on in quickly!' But 欢迎光临 remains the gold standard for polite hospitality.