What is Safari Service worker ? Would disabling it affect website performance?

Question

For the past three days, I have seen Outlook and Twitter service workers trigger randomly, even if I never opened those sites in non-private mode. They consume 2 threads and distract me. Then I force quit them.

Before applying the solution in

• How to disable service workers in Safari 12.1? (Mac)

I need to know

• Why do websites use it?
• What would be the impact if I disable all of them ? (I'd prefer if I can handle it on case by case basis)

Answer 1

Service Workers can be used by web sites to handle functionality such as:

• Enabling Offline mode when you have no Internet connection
• Receiving Push Notifications
• Caching data files for faster load times
• Synchronizing data in the background to provide streaming updates
• Trigger data refreshes based on for example location changes

The impact of disabling the feature depends on the sites involved. Some would just continue working as normal, but perhaps work a tad slower - others would loose functionality, such as offline mode or push notifications - and again others would stop working completely as they insist on that feature working.