If you are a foreigner and staying in someone's apartment in China, you are supposed to register with the police/PSB within 24 hours of your arrival. If you are a resident who has a friend staying you need to tell them this. My son arrived a month ago and I wanted to register him.
It's a pain going to the police station and going through this procedure so many avoid it and do not register. However, now the police and immigration computers are on talking terms it is becoming more necessary. Some people are being asked on exit why they have not registered and a few get comments in their passports or in the system making problems with new visas or future entries.
However Shenzhen Police/PSB have made this much easier using WeChat. First you need to add the Police Official Account - I just searched on Shenzhen in Official Accounts and it's that one with the sort-of arrow. Now add it.
Then you will see the below - No idea what most of it says, but I know which bit to hit and it's that one.
Suddenly you go into English - wow - so you can maybe guess which ones to hit for the next couple of screens till you come to this one where we start the real action. Put in your nationality and passport number - with me so far? Then add a local cell phone number and request the code, which will come through as an sms to enter in the next field. Put in an email address - don't know what it's used for.
Now address - not typed it but got from your flat's QR Code. It seems all flats in Shenzhen have QR Codes - no I didn't know either. Mine is high up to the left of my front door - outside the flat. You scan it and it finds your address - clever isn't it? Once you've done that you get taken to the next screen which requires you to upload a photo of yourself and that's it.
By this time it knows your name - from your passport number, so from the Immigration Computer system - they really are talking to each other, and your address - correct flat number, block number and development name.
A while later you get this.
As far as I know this only works in Shenzhen. I have seen the one for Xi'an and it's just a WeChat implementation of the old paper form.