Web APIs
Beacon API Quiz Exercises
Twelve module-level quizzes covering the full Beacon API series — from the fire-and-forget landscape through the 64 KiB quota, hybrid transports, and fetchLater().
Interactive exercises that help you practice, check your understanding, and find what to revisit.
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Test your knowledge: The Beacon API Landscape
Why sendBeacon exists, what the spec actually says, how it maps onto fetch, and where browsers stand in 2026.
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Exercises
Browse the complete collection and choose the resource that matches what you want to practice or understand.
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ExercisesBeginner
Test your knowledge: The Beacon API Landscape
Why sendBeacon exists, what the spec actually says, how it maps onto fetch, and where browsers stand in 2026.
~6 min read Start exercise -
ExercisesBeginner
Test your knowledge: The Core API
The sendBeacon signature: POST-only, the queueing boolean, silent CORS drops, and the Window-only rule.
~6 min read Start exercise -
ExercisesBeginner
Test your knowledge: Data Types & the CORS Trap
BodyInit types, Content-Type auto-derivation, and the no-cors/cors mode switch behind the JSON-Blob trap.
~6 min read Start exercise -
ExercisesIntermediate
Test your knowledge: The 64 KiB Quota
One shared in-flight pool, what the quota actually charges, in-flight vs lifetime, and the false return.
~6 min read Start exercise -
ExercisesIntermediate
Test your knowledge: Page Lifecycle & Delivery
The hidden state transition, event ordering, unload deprecation, bfcache, and the mobile reality.
~6 min read Start exercise -
ExercisesIntermediate
Test your knowledge: CORS Server-Side
Credentialed beacons, the three response headers, Safari ITP, and preflight failures you never hear about.
~6 min read Start exercise -
ExercisesIntermediate
Test your knowledge: Workers & Interception
Why sendBeacon is Window-only, how Service Workers intercept beacons, and the worker-safe substitute.
~6 min read Start exercise -
ExercisesIntermediate
Test your knowledge: fetch(keepalive)
The functional superset: what it adds, what it lacks, the shared quota, and promise vs boolean.
~6 min read Start exercise -
ExercisesIntermediate
Test your knowledge: Decision Tree & Hybrid Transport
Choosing between sendBeacon and fetch(keepalive), the hybrid pattern, and the shared-quota trap.
~6 min read Start exercise -
ExercisesAdvanced
Test your knowledge: Real-World Patterns
Pageviews, JSON error reports, crash reporting, bfcache analytics, A/B persistence, and the SDK layer.
~6 min read Start exercise -
ExercisesAdvanced
Test your knowledge: fetchLater / Deferred Fetch
The newest transport: the deferred-fetch quota, the activation triggers, activateAfter, and when it complements sendBeacon.
~6 min read Start exercise -
ExercisesAdvanced
Test your knowledge: Testing, Debugging & the Future
Playwright interception, DevTools' missing beacon filter, quota testing, lifecycle timing, and what comes next.
~6 min read Start exercise