Service Worker
A script the browser runs in the background, separate from the web page. Enables offline caching, push notifications, and background sync for progressive web apps.
What is Service Worker?
A script the browser runs in the background, separate from the web page. Enables offline caching, push notifications, and background sync for progressive web apps.
Service Worker is a intermediate-level concept that sits in the Web & Content Delivery area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "Service Worker" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
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Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
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See also
Related glossary terms you might want to look up next.
Caching
Storing frequently accessed data in a faster storage layer so you don't have to fetch it from the original (slower) source every time.
HTTP Caching
Browser and proxy caching controlled by HTTP headers like Cache-Control, ETag, and Last-Modified. Eliminates redundant network requests for unchanged resources.
CDN
A network of servers distributed globally that caches content close to users. Netflix uses CDNs to stream video from servers near you, not from one central location.