Free course

Browser Storage Course

Build reliable browser state with cookies, Web Storage, IndexedDB, Cache Storage, quotas, persistence, and origin-private files.

5 modules · 25 lessons · No signup

Prerequisites: HTML, JavaScript and HTTP

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What you'll learn

Build and test a local-first field-notes app with deliberate storage ownership, safe upgrades, offline resources, export, cleanup, and recovery.

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Course contents

  1. Choose and observe storage

    Map each value’s owner and lifetime, understand browser boundaries, and inspect existing state.

    1. ✓ Follow one piece of data
    2. ✓ Understand origin and site boundaries
    3. ✓ Choose storage from the job
    4. ✓ Inspect before you change
    5. ✓ Check your understanding: choose and observe storage

  2. Cookies over HTTP

    Trace cookie transport, scope values narrowly, secure sessions, and handle partitioned state.

    1. ✓ Follow the cookie round trip
    2. ✓ Control cookie scope and lifetime
    3. ✓ Lock down a session cookie
    4. ✓ Handle cross-site and partitioned cookies
    5. ✓ Check your understanding: cookies over http

  3. Web Storage

    Use localStorage and sessionStorage for small values, then handle invalid data and tab conflicts.

    1. ✓ Save a small preference
    2. ✓ Keep a draft in one tab
    3. ✓ Version and validate stored JSON
    4. ✓ Coordinate tabs and handle failures
    5. ✓ Check your understanding: web storage

  4. IndexedDB

    Store structured notes with keys, indexes, transactions, and versioned schema upgrades.

    1. ✓ Open a notes database
    2. ✓ Write and read structured notes
    3. ✓ Query notes through an index
    4. ✓ Use transactions and unblock upgrades
    5. ✓ Check your understanding: indexeddb

  5. Offline files and durability

    Cache responses, measure quota, request persistence, store files, and design recovery.

    1. ✓ Cache request and response pairs
    2. ✓ Measure quota and request persistence
    3. ✓ Store an attachment in OPFS
    4. ✓ Finish the storage recovery plan
    5. ✓ Check your understanding: offline files and durability