Flutter UpChunk

Flutter UpChunk is a simple port of the JS library https://github.com/muxinc/upchunk done by MUX, Inc.


Add the package to the dependencies section in pubspec.yaml:

  • flutter_upchunk: ^1.5.0 (or latest release)


Add the following import to the .dart file that will use UpChunk

import 'package:flutter_upchunk/flutter_upchunk.dart';


Future<String> _getUploadUrl() {
  String uploadUrl;
  // Perform call either to your API or directly to MUX to retrieve the upload URL
  // ...

  return uploadUrl;

// Chunk upload
var uploadOptions = UpChunkOptions()
  ..endPointResolver = _getUploadUrl()
  ..file = File(_filePath)
  ..onProgress = (progress) {
    print('Upload progress: ${progress.ceil()}%');
  ..onError = (String message, int chunk, int attempts) {
    print('UpChunk error 💥 🙀:');
    print(' - Message: $message');
    print(' - Chunk: $chunk');
    print(' - Attempts: $attempts');
  ..onSuccess = () {
    print('Upload complete! 👋');
var upChunkUpload = UpChunk.createUpload(uploadOptions);


Although the API is a port of the original JS library, some options and properties differ slightly.

createUpload(UpChunkOptions options)

Returns an instance of UpChunk and begins uploading the specified File.

UpChunkOptions parameters:

Upload options
  • endPoint type: string (required if endPointResolver is null)

    URL to upload the file to.

  • endPointResolver type: Future<String> (required if endPoint is null)

    A Future that returns the URL as a String.

  • file type: File (required)

    The file you'd like to upload.

  • headers type: Map<String, String>

    A Map with any headers you'd like included with the PUT request for each chunk.

  • chunkSize type: integer, default:5120

    The size in kb of the chunks to split the file into, with the exception of the final chunk which may be smaller. This parameter should be in multiples of 64.

  • attempts type: integer, default: 5

    The number of times to retry any given chunk.

  • delayBeforeRetry type: integer, default: 1

    The time in seconds to wait before attempting to upload a chunk again.

Event options
  • onAttempt { chunkNumber: Integer, chunkSize: Integer }

    Fired immediately before a chunk upload is attempted. chunkNumber is the number of the current chunk being attempted, and chunkSize is the size (in bytes) of that chunk.

  • onAttemptFailure { message: String, chunkNumber: Integer, attemptsLeft: Integer }

    Fired when an attempt to upload a chunk fails.

  • onError { message: String, chunk: Integer, attempts: Integer }

    Fired when a chunk has reached the max number of retries or the response code is fatal and implies that retries should not be attempted.

  • onOffline

    Fired when the client has gone offline.

  • onOnline

    Fired when the client has gone online.

  • onProgress progress double [0..100]

    Fired continuously with incremental upload progress. This returns the current percentage of the file that's been uploaded.

  • onSuccess

    Fired when the upload is finished successfully.

UpChunk Instance Methods

  • pause()

    Pauses an upload after the current in-flight chunk is finished uploading.

  • resume()

    Resumes an upload that was previously paused.

  • restart()

    Restarts the upload from chunk 0, use only if and after onError was fired.

  • stop()

    Cancels the upload abruptly. restart() can be used to start the upload from chunk 0.


Original code by MUX, Inc. and ported to Dart 🎯 with ❤ by a Flutter developer.