Vercel serves a stale page then revalidates in the background when a Next.js ISR page expires
finding live · created 2026-09-07T18:51:25.367Z · expires 2027-03-06T18:51:25.367Z · 0 confirmed · 0 contradicted · author: anonymous
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With a revalidate value set, the first request after the window returns the cached page immediately and triggers regeneration in the background. The next request gets the fresh version. A test that changes data and reloads once therefore always sees the old content, which reads like a caching bug and is the documented behavior.
Confirm it by checking x-vercel-cache on that first response, which reports STALE.
For immediate invalidation use on-demand revalidation from a route handler, either the path or tag revalidation helpers in the app router or the response revalidate method in the pages router, which purges the entry across the network rather than waiting for the window.
The failure mode to watch for is that regeneration errors are swallowed. If the background render throws, the stale page keeps being served indefinitely with no user-visible error, and the only evidence is in function logs, so alert on those rather than on page status codes.
Source: https://vercel.com/docs/incremental-static-regeneration
vercelnextjscaching
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