Handling Multipart/Form-Data in Next.js | Updated 2024

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When building web applications, handling file uploads is a common requirement. Next.js, a popular React framework, can handle file uploads using multipart/form-data. This article will guide you through setting up file uploads in a Next.js application.

Prerequisites

Before we start, ensure you have the following:

• Node.js installed
• Basic knowledge of Next.js and React
• A Next.js project setup. If not, you can create one using:

npx create-next-app@latest
cd your-nextjs-app

Steps for Handling Multipart/Form-Data in Next.js

Step 1: Install Dependencies

We’ll need a few packages to handle file uploads and parse multipart/form-data:

• formidable for parsing form data
• fs for interacting with the file system

Install these packages using npm or yarn:

npm install formidable

or

yarn add formidable

Step 2: Create an API Route for File Upload

Next.js allows you to create API routes in the pages/api directory. Let’s create a route to handle file uploads.

Create a new file at pages/api/upload.js:

import formidable from 'formidable';
import fs from 'fs';
import path from 'path';

// Set the config for formidable
export const config = {
  api: {
    bodyParser: false,
  },
};

const uploadDir = path.join(process.cwd(), '/public/uploads');

const ensureDir = dir => {
  if (!fs.existsSync(dir)) {
    fs.mkdirSync(dir, { recursive: true });
  }
};

const uploadFile = async (req, res) => {
  ensureDir(uploadDir);
 
  const form = new formidable.IncomingForm();
  form.uploadDir = uploadDir;
  form.keepExtensions = true;
 
  form.parse(req, (err, fields, files) => {
    if (err) {
      return res.status(500).json({ error: err.message });
    }
   
    const filePath = files.file.filepath;
    const fileName = files.file.originalFilename;

    fs.rename(filePath, path.join(uploadDir, fileName), (err) => {
      if (err) {
        return res.status(500).json({ error: err.message });
      }
     
      res.status(200).json({ message: 'File uploaded successfully' });
    });
  });
};

export default uploadFile;

Step 3: Create a File Upload Form

Create a simple form to allow users to upload files. Add the following code to a new file at pages/index.js:

import { useState } from 'react';

export default function Home() {
  const [file, setFile] = useState(null);

  const handleFileChange = (e) => {
    setFile(e.target.files[0]);
  };

  const handleSubmit = async (e) => {
    e.preventDefault();

    const formData = new FormData();
    formData.append('file', file);

    const res = await fetch('/api/upload', {
      method: 'POST',
      body: formData,
    });

    if (res.ok) {
      alert('File uploaded successfully');
    } else {
      alert('Failed to upload file');
    }
  };

  return (
    <div>
      <h1>Upload a File</h1>
      <form onSubmit={handleSubmit}>
        <input type="file" onChange={handleFileChange} />
        <button type="submit">Upload</button>
      </form>
    </div>
  );
}

Step 4: Update Next.js Configuration

Make sure your Next.js configuration allows for file uploads and serving static files from the public/uploads directory.

Update your next.config.js file:

const path = require('path');

module.exports = {
  // Other configurations...
  webpack: (config, { isServer }) => {
    if (isServer) {
      require('./scripts/generate-sitemap');
    }
   
    config.module.rules.push({
      test: /\.(png|jpe?g|gif|mp3|wav|ogg|ttf|woff|woff2|eot|otf|svg)$/,
      loader: 'file-loader',
      options: {
        publicPath: '/_next/static/media',
        outputPath: 'static/media',
        name: '[name].[hash].[ext]',
      },
    });

    return config;
  },
};

Step 5: Test Your Implementation

Start your Next.js development server:

npm run dev

or

yarn dev

Open your browser and navigate to http://localhost:3000. You should see the file upload form. Try uploading a file and ensure it’s correctly saved in the public/uploads directory.

Conclusion

In this article, we covered how to handle multipart/form-data in Next.js by creating an API route to handle file uploads using formidable and fs. We also built a simple file upload form in a Next.js page to test our implementation. With these steps, you can now handle file uploads in your Next.js applications.

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Handling Multipart/Form-Data in Next.js – FAQs