Custom Next.js Cache Handler

You can configure the Next.js cache location if you want to persist cached pages and data to durable storage, or share the cache across multiple containers or instances of your Next.js application.

Good to know: The cacheHandler (singular) configuration is specifically used by Next.js for server cache operations such as storing and revalidating ISR, route handler responses, and optimized images. It is not used by 'use cache' directives. For 'use cache' directives, use cacheHandlers (plural) instead. cacheMaxMemorySize is separate from both, and sizes the in-memory cache for each.

module.exports = {
  cacheHandler: require.resolve('./cache-handler.js'),
  cacheMaxMemorySize: 0, // disable default in-memory caching
}

View an example of a custom cache handler and learn more about the implementation.

API Reference

The cache handler can implement the following methods: get, set, revalidateTag, and resetRequestCache.

get()

The ctx parameter contains a kind property that indicates the type of cache entry being retrieved. Possible values include 'APP_PAGE', 'APP_ROUTE', 'PAGES', 'FETCH', and 'IMAGE'.

Cache keys are opaque identifiers. Preserve the entire key when reading and writing entries; a key is not a request pathname.

Response keys include the response kind and a SHA-256 hash of the source route to keep different routes from sharing entries. Pages Router sources use the route definition's canonical pathname, so an index module has the same identity in both bundlers. App Router sources use the full page module name, including route groups and parallel slots. For example, a Pages Router response for /blog/post generated by /blog/[slug] uses /route-cache/PAGES/<route-hash>/$/blog/post, where <route-hash> is the 64-character hexadecimal SHA-256 digest of the UTF-8 source string /blog/[slug]. This bounds the added directory depth and avoids expanding Unicode source names on disk. The request pathname remains readable; the source route cannot be recovered from its hash. Handlers that previously interpreted keys as pathnames must account for this namespace. Fetch cache keys are unchanged.

Without a build adapter, prerendered responses remain at their historical server/pages and server/app paths. Their metadata identifies the exact scoped key, source owner, and fallback status that produced each immutable build seed. The built-in filesystem cache verifies that metadata before reading a historical seed, then promotes the complete response to server/route-cache while retaining the original artifact and its age. When an adapter is configured, build-time response artifacts are written directly to their scoped server/route-cache keys so colliding routes cannot overwrite one another before the adapter packages them. Static output: 'export' continues to emit normal public export files. Runtime reads and writes use only scoped keys. Custom cache handlers receive the opaque scoped key and are never queried with a historical pathname; an external response cache must preserve that key unchanged.

Runtime packaging must preserve the existing source-route metadata in the prerender manifest. Next.js also uses it to verify the allowed parameters and rendering mode of the selected route.

Integrations that read cached responses before invoking Next.js must also preserve source-route ownership when selecting entries. Removing the route namespace or falling back to pathname-only cache entries defeats that isolation.

Returns the cached value or null if not found.

set()

The data object contains a kind property that indicates the type of cache entry. For image optimization, kind will be 'IMAGE' and the data will include properties like buffer, etag, extension, and revalidate.

Returns Promise<void>.

revalidateTag()

Returns Promise<void>. Learn more about revalidating data or the revalidateTag() function.

resetRequestCache()

This method resets the temporary in-memory cache for a single request before the next request.

Returns void.

Good to know:

• revalidatePath is a convenience layer on top of cache tags. Calling revalidatePath will call your revalidateTag function, which you can then choose if you want to tag cache keys based on the path.

Image Optimization Caching

The cacheHandler can also be used for caching optimized images from next/image. To enable this, set images.customCacheHandler to true in your next.config.js:

module.exports = {
  cacheHandler: require.resolve('./cache-handler.js'),
  images: {
    customCacheHandler: true,
  },
}

Good to know: This opt-in flag will become the default behavior in the next major version. Setting it now allows you to prepare your cache handler for image optimization entries.

You can use the kind property to differentiate between cache entry types and handle images separately if needed, for example to implement an eviction policy or store images in a different location.

When handling image cache entries, the kind will be 'IMAGE' and the data will include buffer, etag, extension, and revalidate properties.

Platform Support

Learn how to configure ISR when self-hosting Next.js.

Version History