Chunked Uploads

Upload large files by splitting them into smaller chunks. This enables:

• Upload of files larger than server limits
• Resumable uploads after network failures
• Better progress tracking
• Reduced memory usage

Basic Chunked Upload

import { useDropup, createChunkedUploader } from '@samithahansaka/dropup';

function ChunkedUploader() {
  const { files, actions, state, getDropProps, getInputProps } = useDropup({
    upload: createChunkedUploader({
      url: '/api/upload/chunk',
      chunkSize: 5 * 1024 * 1024, // 5MB chunks
    }),
  });

  return (
    <div>
      <div {...getDropProps()} style={styles.dropzone}>
        <input {...getInputProps()} />
        <p>Drop large files here - they'll upload in chunks</p>
      </div>

      {files.map(file => (
        <div key={file.id} style={styles.fileItem}>
          <span>{file.name}</span>
          <span>{(file.size / 1024 / 1024).toFixed(1)} MB</span>

          {file.status === 'uploading' && (
            <div style={styles.progressBar}>
              <div
                style={{
                  ...styles.progress,
                  width: `${file.progress}%`,
                }}
              />
            </div>
          )}

          <span>{file.status}</span>
        </div>
      ))}

      <button
        onClick={() => actions.upload()}
        disabled={state.isUploading}
      >
        Upload
      </button>
    </div>
  );
}

const styles = {
  dropzone: {
    border: '2px dashed #ccc',
    borderRadius: 8,
    padding: 40,
    textAlign: 'center' as const,
    marginBottom: 20,
  },
  fileItem: {
    display: 'flex',
    alignItems: 'center',
    gap: 12,
    padding: 12,
    borderBottom: '1px solid #eee',
  },
  progressBar: {
    flex: 1,
    height: 8,
    backgroundColor: '#eee',
    borderRadius: 4,
    overflow: 'hidden',
  },
  progress: {
    height: '100%',
    backgroundColor: '#4caf50',
    transition: 'width 0.2s',
  },
};

Chunked Upload Options

createChunkedUploader({
  // Required
  url: '/api/upload/chunk',

  // Optional settings
  chunkSize: 5 * 1024 * 1024,  // 5MB (default)
  concurrency: 3,              // Parallel chunks (default: 1)
  retries: 3,                  // Retry failed chunks (default: 3)

  // Headers for all chunk requests
  headers: {
    'Authorization': 'Bearer token',
  },

  // Custom chunk metadata
  getChunkMeta: (file, chunkIndex, totalChunks) => ({
    fileId: file.id,
    fileName: file.name,
    chunkIndex,
    totalChunks,
  }),
});

Server-Side Handling

Your server needs to handle chunk uploads and reassemble them.

Example: Node.js/Express

const express = require('express');
const multer = require('multer');
const fs = require('fs');
const path = require('path');

const app = express();
const upload = multer({ dest: 'chunks/' });

const uploadState = new Map();

app.post('/api/upload/chunk', upload.single('chunk'), (req, res) => {
  const { fileId, fileName, chunkIndex, totalChunks } = req.body;

  // Store chunk info
  if (!uploadState.has(fileId)) {
    uploadState.set(fileId, {
      fileName,
      totalChunks: parseInt(totalChunks),
      chunks: [],
    });
  }

  const state = uploadState.get(fileId);
  state.chunks.push({
    index: parseInt(chunkIndex),
    path: req.file.path,
  });

  // Check if all chunks received
  if (state.chunks.length === state.totalChunks) {
    // Sort chunks by index
    state.chunks.sort((a, b) => a.index - b.index);

    // Combine chunks
    const finalPath = path.join('uploads', fileName);
    const writeStream = fs.createWriteStream(finalPath);

    for (const chunk of state.chunks) {
      const data = fs.readFileSync(chunk.path);
      writeStream.write(data);
      fs.unlinkSync(chunk.path); // Clean up chunk
    }

    writeStream.end();
    uploadState.delete(fileId);

    return res.json({
      complete: true,
      url: `/uploads/${fileName}`,
    });
  }

  res.json({
    complete: false,
    received: state.chunks.length,
    total: state.totalChunks,
  });
});

tus Protocol

For robust resumable uploads, use the tus protocol:

import { useDropup } from '@samithahansaka/dropup';
import { createTusUploader } from '@samithahansaka/dropup/tus';

function TusUploader() {
  const { files, actions, state, getDropProps, getInputProps } = useDropup({
    upload: createTusUploader({
      endpoint: 'https://tusd.tusdemo.net/files/',

      // Optional settings
      chunkSize: 5 * 1024 * 1024,
      retryDelays: [0, 1000, 3000, 5000],

      // Metadata for the server
      metadata: {
        filetype: 'file.type',
        filename: 'file.name',
      },

      // Resume from localStorage
      storeFingerprintForResuming: true,
    }),

    onUploadComplete: (file) => {
      console.log('tus upload complete:', file.uploadedUrl);
    },
  });

  return (
    <div>
      <div {...getDropProps()} style={styles.dropzone}>
        <input {...getInputProps()} />
        <p>Drop files for resumable upload</p>
      </div>

      {files.map(file => (
        <div key={file.id} style={styles.fileItem}>
          <span>{file.name}</span>
          <span>{file.progress}%</span>
          <span>{file.status}</span>
        </div>
      ))}

      <button onClick={() => actions.upload()}>
        Upload
      </button>
    </div>
  );
}

Pause and Resume

With chunked uploads, you can pause and resume:

function PausableUploader() {
  const { files, actions, getDropProps, getInputProps } = useDropup({
    upload: createChunkedUploader({
      url: '/api/upload/chunk',
    }),
  });

  return (
    <div>
      <div {...getDropProps()}>
        <input {...getInputProps()} />
        <p>Drop files here</p>
      </div>

      {files.map(file => (
        <div key={file.id}>
          <span>{file.name}</span>
          <span>{file.progress}%</span>
          <span>{file.status}</span>

          {file.status === 'uploading' && (
            <button onClick={() => actions.cancel(file.id)}>
              Pause
            </button>
          )}

          {file.status === 'paused' && (
            <button onClick={() => actions.retry([file.id])}>
              Resume
            </button>
          )}
        </div>
      ))}

      <button onClick={() => actions.upload()}>
        Start All
      </button>
    </div>
  );
}

Progress Tracking with Chunks

import { useState } from 'react';

function DetailedChunkProgress() {
  const [chunkProgress, setChunkProgress] = useState<Map<string, number[]>>(
    new Map()
  );

  const { files, actions, getDropProps, getInputProps } = useDropup({
    upload: createChunkedUploader({
      url: '/api/upload/chunk',
      chunkSize: 1024 * 1024, // 1MB chunks for visibility

      onChunkProgress: (file, chunkIndex, progress) => {
        setChunkProgress(prev => {
          const next = new Map(prev);
          const fileProgress = next.get(file.id) || [];
          fileProgress[chunkIndex] = progress;
          next.set(file.id, fileProgress);
          return next;
        });
      },
    }),
  });

  return (
    <div>
      <div {...getDropProps()} style={styles.dropzone}>
        <input {...getInputProps()} />
        <p>Drop files here</p>
      </div>

      {files.map(file => {
        const chunks = chunkProgress.get(file.id) || [];
        const totalChunks = Math.ceil(file.size / (1024 * 1024));

        return (
          <div key={file.id} style={styles.fileCard}>
            <p>{file.name}</p>

            {/* Chunk progress visualization */}
            <div style={styles.chunkGrid}>
              {Array.from({ length: totalChunks }).map((_, i) => (
                <div
                  key={i}
                  style={{
                    ...styles.chunkBlock,
                    backgroundColor: chunks[i] === 100
                      ? '#4caf50'
                      : chunks[i] > 0
                      ? '#8bc34a'
                      : '#eee',
                  }}
                  title={`Chunk ${i + 1}: ${chunks[i] || 0}%`}
                />
              ))}
            </div>

            <p>Overall: {file.progress}%</p>
          </div>
        );
      })}

      <button onClick={() => actions.upload()}>
        Upload
      </button>
    </div>
  );
}

const styles = {
  dropzone: {
    border: '2px dashed #ccc',
    padding: 40,
    textAlign: 'center' as const,
    marginBottom: 20,
  },
  fileCard: {
    padding: 16,
    border: '1px solid #eee',
    borderRadius: 8,
    marginBottom: 12,
  },
  chunkGrid: {
    display: 'flex',
    flexWrap: 'wrap' as const,
    gap: 4,
    margin: '12px 0',
  },
  chunkBlock: {
    width: 20,
    height: 20,
    borderRadius: 4,
    transition: 'background-color 0.2s',
  },
};

Chunk Size Recommendations

File Size	Recommended Chunk Size
< 10 MB	No chunking needed
10-100 MB	5 MB
100 MB - 1 GB	10 MB
> 1 GB	20-50 MB

Performance

Larger chunks = fewer requests, but longer recovery on failure. Smaller chunks = more overhead, but better resumability.