Make Astro work offline
InstantPWA hosts a fallback service worker and manifest for Astro, so pages you've already visited keep working offline without you writing cache logic yourself. Add the snippet to src/layouts/BaseLayout.astro via BaseLayout.astro <head> and the worker registers automatically on first visit.
Steps
- 1
Open src/layouts/BaseLayout.astro
Go to BaseLayout.astro <head>.
- 2
Paste the InstantPWA snippet
Drop the one-line async script tag in the Astro head section — no build step or dependency install.
- 3
Let the service worker register
No manifest.json or sw.js to write — InstantPWA serves both and scopes the worker to your site's root.
- 4
Test offline mode
Visit a page once, then use DevTools → Network → Offline (or airplane mode on a phone) and reload to confirm cached pages still render.
- 5
Verify on a phone
Open your live Astro URL on a mobile device (not the editor preview) to confirm the popup renders.
Constraints to know
- Astro ships zero JS by default (the 'islands' architecture), so InstantPWA is often the only client-side script on the page — it doesn't need a hydration directive like client:load.
- If you use Astro's View Transitions (astro:transitions), the <head> persists across client-side navigations, so the snippet keeps its state instead of re-running per page.
FAQ
Do I need to write my own service worker?+
No — InstantPWA hosts a fallback manifest and service worker automatically if your site doesn't already ship one.
What happens to pages I haven't visited yet?+
They won't be available offline until visited at least once — InstantPWA caches on-visit rather than pre-caching your entire site.
Does offline mode change how Astro serves pages normally?+
No — the service worker only intercepts requests when the browser is offline; online visits behave exactly as before.