Foreigners entering China for the first time if they are not staying at a hotel. After that, you don't need to do it again if you live here on a resident permit, unless you stay at a different address or use a different passport.

Here's the link: Self-Help Declaration System For Overseas Personnel's Accommodation Registration.

This website is only valid for people registering at an address in Shanghai. Assuming you don't have an account, make one. It takes two seconds and doesn't require an email verification (but you might want that email for later).

The next step is to fill in your info, once you click off the thoughtful "you don't need to register if you stay in a hotel" tip. This might be the most foreign user-friendly website the government has ever made.

Just upload an image of the photo ID page in your passport. It'll pick the details out automatically, but you can add or correct anything that wasn't right.

Don't mind the "with your certificate" bit, just upload a passport photo or a clean, passport-style selfie. I did it at my desk. The address system is a slight pain in the butt, owing to the interminable difficulty in translating sometimes complex Chinese addresses into English ones. Do your best. Trust us. We know all about that.

Note: the "Date of Departure" info doesn't appear on your final certificate, just put the last date you left China.

[Update: or, if it's your first time, the day you plan to leave the country, for example when your visa ends.]

Now you just wait!

Processing can take five to ten minutes.

[Update: apparently it can take much longer sometimes.]

You'll get an email confirmation when it's done, and it might show up in your spam folder.

Back on the website, select the QR code that's replaced the "processing" bit and you'll have the option to "preview" (download), email, or share a PDF of your form, with chop, filled in for you. Magic!

Just in case you can't do it online, you can, of course, go to the nearest police station and do it there. Here's how you find it:

Open your preferred maps app, such as Baidu Maps or Gaode Maps. Type in "派出所" (pai chu suo), and you'll be presented with a list of nearby police stations, sorted by distance. Choose the closest one, and you're all set!