Web applications with application-like behaviour.
WHAT THEY PROVIDE
Installation to the device Working offline, or with poor connectivity Background updating Notifications, where permitted
WHAT THEY REQUIRE
A secure connection A manifest describing the application A service worker
WHAT A SERVICE WORKER IS
A script running separately from the page, able to intercept network requests.
WHAT THAT ENABLES
Serving cached content when offline Controlling what is cached and for how long Background work
WHY THAT MATTERS PARTICULARLY HERE
Connectivity varies, and data is metered.
An application that works offline and transfers less is genuinely more useful.
WHAT TO CACHE
The application shell Assets that change rarely
WHAT TO BE CAREFUL WITH
Serving stale content indefinitely Caching responses that should be current Updating the service worker, which requires care
WHY THAT LAST ONE
A faulty service worker can make a site unreachable until it is replaced.
WHAT TO TEST
Behaviour offline, and on a slow connection.
