First published on tychelabs.net .

Your developer has stopped replying and the app is still live? Here are the 12 things an app depends on, in the order we check them when we take one over.

The message usually arrives as a question with a hidden emergency inside it. "Our developer isn't replying. Can you update our app?" Sometimes the developer has moved on, sometimes the agency has closed, sometimes there was a falling out. The app is still in the store and still being used, which is why nobody noticed how much of it lives in someone else's accounts.

We take over apps like this, and the first thing we do is the same every time: go through a list of everything the app depends on and find out who controls each one. This guide is that list, in the order we work through it, with what to check, what good looks like and what to do when the answer is "we don't know".…