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Service workers & PWAs

Service workers & PWAs

Service workers from first principles — lifecycle, fetch interception, caching strategies, and the manifest pieces that turn a site into something installable.

~ 165 min·11 lessons·updated may 2026

What you'll learn


Lessons

Read in order. Each lesson stands on its own, but the order is deliberate.

11 lessons · ~157 min total

  1. 01
    What a PWA is in 2026
    Installable, capable, network-aware — and what it isn't.
    13 min
  2. 02
    The service worker lifecycle
    install, activate, fetch — and the states in between that confuse everyone.
    16 min
  3. 03
    Registering and updating workers
    Why your changes don't show up, and how to make them.
    14 min
  4. 04
    Fetch interception
    respondWith, the Request/Response duo, and the cost of getting it wrong.
    15 min
  5. 05
    Caching strategies
    cache-first, network-first, stale-while-revalidate — pick by intent.
    17 min
  6. 06
    The web app manifest
    Icons, names, scope, display modes, and what each line buys.
    12 min
  7. 07
    Install prompts
    beforeinstallprompt, the criteria the browser checks, and the UX of asking.
    13 min
  8. 08
    Push and background sync
    Notifications and queued work — what's reliable, what isn't.
    16 min
  9. 09
    Offline-first design
    Designing UI that admits the network might not be there.
    14 min
  10. 10
    Workbox without the magic
    What Workbox actually generates, and the cost of pretending it's free.
    14 min
  11. 11
    Debugging service workers
    DevTools Application panel, the unregister button, and the order to check things.
    13 min

Prerequisites

  • · Comfortable with promises and the fetch API
  • · Know the basics of HTTP caching

After this, try