← PWA & Install
Offline Support
Probing…Offline Support is a web platform capability in the PWA & Install category. Service worker + Cache API together make this site work offline. Supported in Chromium 40+, Firefox 44+, and Safari 11.1+. Requires a secure context (HTTPS or localhost).
Secure context
Try it
Loading demo…
Code
const names = await caches.keys()
const cache = await caches.open(names[0])
const entries = await cache.keys()
console.log(entries.length, 'precached responses')
const { usage, quota } = await navigator.storage.estimate()
console.log(usage, '/', quota, 'bytes')Browser support
Chromium
40
Firefox
44
Safari
11.1
Frequently asked questions
Which browsers support Offline Support?
Supported in Chromium 40+, Firefox 44+, and Safari 11.1+.
Does Offline Support require HTTPS?
Yes. Offline Support needs a secure context, so it only works over HTTPS (or on localhost during development).
What is Offline Support used for?
Service worker + Cache API together make this site work offline.
Can I try Offline Support in my browser?
Yes. shwcs.net runs a live Offline Support demo that probes your current browser and lets you try the API. Everything runs locally — nothing is sent anywhere.