vercel/swr · error

Missing pre-initiated data for serialized key "${key}" durin

Error message

Missing pre-initiated data for serialized key "${key}" during server-side rendering. Data fetching should be initiated on the server and provided to SWR via fallback data. You can set "strictServerPrefetchWarning: false" to disable this warning.

What it means

Error "Missing pre-initiated data for serialized key "${key}" during server-side rendering. Data fetching should be initiated on the server and provided to SWR via fallback data. You can set "strictServerPrefetchWarning: false" to disable this warning." thrown in vercel/swr.

Source

Thrown at src/index/use-swr.ts:434

      },
      () => {
        hydrationRef.current = true
        return hydrationRef
      }
    )
  const isHydration = hydrationRef.current
  // During the initial SSR render, warn if the key has no data pre-fetched via:
  // - fallback data
  // - preload calls
  // - initial data from the cache provider
  // We only warn once for each key during Hydration.
  if (
    strictServerPrefetchWarning &&
    isHydration &&
    !suspense &&
    hasKeyButNoData
  ) {
    console.warn(
      `Missing pre-initiated data for serialized key "${key}" during server-side rendering. Data fetching should be initiated on the server and provided to SWR via fallback data. You can set "strictServerPrefetchWarning: false" to disable this warning.`
    )
  }

  // Resolve the default validating state:
  // If it's able to validate, and it should revalidate when mount, this will be true.
  // - Suspense mode and there's stale data for the initial render.
  // - Not suspense mode and there is no fallback data and `revalidateIfStale` is enabled.
  // - `revalidateIfStale` is enabled but `data` is not defined.
  const shouldDoInitialRevalidation = (() => {
    if (!key || !fetcher) return false
    // If it's paused, we skip revalidation.
    if (getConfig().isPaused()) return false
    // if a key already has revalidators and also has error, we should not trigger revalidation
    if (hasRevalidator && !isUndefined(error)) return false
    // If `revalidateOnMount` is set, we take the value directly.
    if (isInitialMount && !isUndefined(revalidateOnMount))
      return revalidateOnMount

View on GitHub (pinned to 7173e55b2a)

When it happens

Trigger: Thrown at src/index/use-swr.ts:434 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of vercel/swr@7173e55b2a (2026-08-27). Data as JSON: /api/errors/ce1adf93128a2212. Report an issue: GitHub.