stale-while-revalidate
PerformanceDefined term
stale-while-revalidate, defined in RFC 5861, extends Cache-Control with a grace window: after a response's freshness lifetime expires, a cache may keep serving it for the stated number of seconds while it revalidates with the origin in the background.
The reader-visible effect is that repeat visits stay instant while content stays approximately fresh — latency is paid by the cache, not the user. CDNs and service workers implement the same pattern, and application frameworks borrow the name for identical data-fetching semantics.
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Performance7 of 28 terms
- Largest Contentful Paint (LCP)⦿ liveThe render time of the largest visible content element — the loading-speed Core Web Vital. Good ≤ 2.5 s at p75.Performance
- Interaction to Next Paint (INP)⦿ liveThe responsiveness Core Web Vital: full interaction latency through the next visual update. Replaced FID in 2024. Good ≤ 200 ms.Performance
- Cumulative Layout Shift (CLS)⦿ liveThe visual-stability Core Web Vital: the largest session window of unexpected layout shifts. Good ≤ 0.1.Performance
- Time to First Byte (TTFB)⦿ liveElapsed time from navigation start until the first byte of the response arrives — the server and network's share of loading delay.Performance
- Render-blocking resourceA stylesheet or synchronous script the browser must fetch and process before it can paint — a direct LCP tax.Performance
- stale-while-revalidateA Cache-Control extension (RFC 5861) that serves an expired cached response instantly while refreshing it in the background.Performance
- 75th percentile (p75)⦿ liveThe assessment point for Core Web Vitals field data: the experience at least three quarters of page loads meet or beat.Performance