Nextjs API File Upload

Next.js API File Upload (App Router)

This project uses Next.js App Router. File upload in API routes must use Next.js built-in handling, not Express middleware.

Do Not Use

• Express middleware (e.g. multer) in API routes. It can block the request pipeline and cause long hangs (e.g. login or upload appearing stuck).

Do Use

• request.formData() in the route handler.
• Stream or parse the file (e.g. CSV) inside the handler after calling formData().

Example Pattern

// In app/api/upload/route.ts (or similar)
export async function POST(request: Request) {
  const formData = await request.formData();
  const file = formData.get('file') as File | null;
  if (!file) return Response.json({ error: 'No file' }, { status: 400 });
  // Parse/stream file in handler (e.g. CSV parsing)
  // ...
}

Integration

• Can be merged into a broader "Next.js API" skill if one exists. Use for any task that adds or changes file upload in Next.js App Router API routes.