How the parts communicate.
WHAT THE SERVICE WORKER DOES
Handles events, coordinates, and communicates with servers.
WHAT IS DIFFERENT ABOUT IT
It terminates when idle, and restarts on the next event.
WHAT THAT MEANS
Anything held in a variable is lost.
WHAT TO DO ABOUT IT
Persist state in storage, and read it when needed.
WHAT CONTENT SCRIPTS DO
Run within a page, able to read and modify it.
WHAT THEY CANNOT DO
Access most extension capabilities directly.
HOW THEY COMMUNICATE
By sending messages to the service worker.
WHAT TO DESIGN
A clear message protocol between components.
WHAT TO BE CAREFUL WITH
Content scripts conflicting with the page's own scripts Assuming a page's structure, which changes Injecting into pages where you were not intended
WHAT ISOLATION MEANS
Content scripts share the page's document but not its script environment.
WHY THAT MATTERS
You cannot directly call the page's own functions, and vice versa.
WHAT TO USE FOR STORAGE
The extension storage, which synchronises or stays local.
WHAT TO NEVER STORE THERE
Secrets, which are readable.
