Resolving 500 errors when uploading large files through Next.js API routes

If you're experiencing 500 internal server errors when uploading files larger than 10MB through Next.js API routes, this is typically caused by configuration issues with Next.js body size limits and runtime settings. Common symptoms 500 internal server errors when uploading files over 10MB Uploads work locally but fail in deployed environments Error messages like "Request body exceeded 10MB" or "Part terminated early due to unexpected end of multipart data" No detailed error logs appearing in your application logs Solution To resolve this issue, you need to configure both the body size limit and runtime settings in your Next.js application:

1. Set the body size limit in next.config.js Add or update your next.config.js file to include a higher body size limit: module.exports = { experimental: { serverActions: { bodySizeLimit: '100mb', }, }, }

2. Configure the API route runtime In your upload API route file, ensure you're using the Node.js runtime instead of the edge runtime: export const runtime = 'nodejs' The edge runtime is not ideal for handling large file uploads and can cause these types of errors.

3. Deploy and test After making these changes, redeploy your application and test the file upload functionality. Alternative recommendation For better performance and reliability with large file uploads, consider implementing direct-to-S3 uploads using AWS pre-signed URLs instead of routing uploads through your Next.js API routes. This approach is recommended by AWS and reduces the load on your application servers. Additional troubleshooting If you continue to experience issues: Check that your route configuration properly matches the upload endpoints Add additional logging to your API routes to help identify where the upload process is failing Consider using multipart uploads for files larger than 100MB