expireTime

expireTime?: number

expireTime changes the stale-while-revalidate figure Next.js writes into the Cache-Control header for ISR pages. It does not change when Next.js regenerates a page — your route's revalidate period still does that. It changes how long a shared cache in front of your app may keep serving the old copy while the new one is fetched.

How the number is derived

The header is computed per route from both values: the revalidate period becomes s-maxage, and stale-while-revalidate becomes the expire time minus that period. With a 15-minute revalidate and expireTime: 3600, Next.js sends:

Cache-Control: s-maxage=900, stale-while-revalidate=2700

When to reach for it

Raise it when your origin is expensive or occasionally slow and you would rather a CDN serve a slightly old page than queue requests behind a regeneration. Lower it when stale content is a correctness problem — pricing, stock levels, anything legally sensitive.

What trips people up

• It is a global default, not a per-route knob. Routes differ only through their own revalidate periods.
• Set it below a route's revalidate period and the subtraction leaves no useful stale window at all.
• It is only a header. A CDN that ignores stale-while-revalidate ignores this.

import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  // one hour in seconds
  expireTime: 3600,
}

export default nextConfig

// next.config.ts
import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  expireTime: 3600, // one hour
}

export default nextConfig

// app/blog/[slug]/page.tsx
export const revalidate = 900 // fifteen minutes

export default async function Page(props: PageProps<'/blog/[slug]'>) {
  const { slug } = await props.params
  return <h1>{slug}</h1>
}

// Response header for this route:
// Cache-Control: s-maxage=900, stale-while-revalidate=2700

import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  // five minutes in seconds
  expireTime: 300,
}

export default nextConfig

import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  expireTime: process.env.VERCEL_ENV === 'production' ? 86_400 : 60,
}

export default nextConfig