vercel/next.js · error

Saving heap snapshot to ${heapFilename}. Note: this will ta

Error message

Saving heap snapshot to ${heapFilename}.  Note: this will take some time.

What it means

traceMemoryUsage warns the first time heap usage crosses the threshold that it is synchronously writing a V8 heap snapshot to distDir/<description>.heapsnapshot; the note about timing exists because snapshot writing can take a while on large heaps.

Source

Thrown at packages/next/src/lib/memory/trace.ts:109

    info(` - Percentage Heap Used: ${percentageHeapUsed.toFixed(2)}%`)
    info('***************************************')
    info('')

    if (percentageHeapUsed > HEAP_SNAPSHOT_THRESHOLD_PERCENT) {
      const distDir = traceGlobals.get('distDir')
      const heapFilename = join(
        distDir,
        `${description.replace(' ', '-')}.heapsnapshot`
      )
      warn(
        bold(
          `Heap usage is close to the limit. ${percentageHeapUsed.toFixed(
            2
          )}% of heap has been used.`
        )
      )
      if (!alreadyGeneratedHeapSnapshot) {
        warn(
          bold(
            `Saving heap snapshot to ${heapFilename}.  ${italic(
              'Note: this will take some time.'
            )}`
          )
        )
        v8.writeHeapSnapshot(heapFilename)
        alreadyGeneratedHeapSnapshot = true
      } else {
        warn(
          'Skipping heap snapshot generation since heap snapshot has already been generated.'
        )
      }
    }
  }
}

View on GitHub (pinned to 0eb3775416)

Solutions

1. Wait while the heap snapshot is written to disk, then analyze it with Chrome DevTools or similar.

When it happens

Trigger: Thrown at packages/next/src/lib/memory/trace.ts:109 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of vercel/next.js@0eb3775416 (2026-08-19). Data as JSON: /api/errors/1ef601c3f553eab2. Report an issue: GitHub.