Every Drupal developer knows the following error message (maybe some by heart): The content has been modified by another user, changes cannot be saved. In Drupal 8 the message is even a bit longer: The content has either been modified by another user, or you have already submitted modifications. As a result, your changes cannot be saved. While this inbuilt mechanism is very useful to preserve data integrity, the only way to get rid of the message is to reload the form and then redo the changes you want to make.
A native mobile application which can cache the data locally is a way to make content available offline. However, not everyone has the time and/or money to create a dedicated app, and frankly, it's not always an additional asset. What if browsers could work without network connection but still serve content: Application Cache and/or Service Workers to the rescue!
This is not a post about caching for applications, but a different kind, the kind where people all over the world hide artifacts and you must search and log them. Welcome to the world of Geocaching!
Note: this patch is quite old, so be aware there might be errors on the latest version on chosen.