EvaporateJS: The Power of Browser to S3 Multipart Resumable Uploads


A Complete File Upload API for AWS S3

Evaporate is a JS library for uploading files from a browser to AWS S3, using parallel S3's multipart uploads with MD5 checksum support and control over pausing / resuming the upload.

Help us test our v3!

We're in the final stages of migrating the library to Typescript and Webpack, and we're doing it to increase the maintainability of the project, but we also had reports of increased performance and lower memory usage!

The new version will foster an increase in the ease of contributing and onboarding of new maintainers.

But don't worry, as there were no contract changes, if you're using our v2 it should work out of the box.

To test it, it's very simple, you just have to install the library like this:

npm install evaporate@TTLabs/EvaporateJS#pull/448/head

And that's it! It should immediately work. If you have some feedback about it, please post it here.



Configurable number of parallel uploads for each part (maxConcurrentParts)

Configurable MD5 Checksum calculations and handling for each uploaded part (computeContentMd5)

Pluggable signing methods with customAuthMethod to support AWS Lambda, async functions and more.


S3 Transfer Acceleration (s3Acceleration)

Robust recovery when uploading huge files. Only parts that have not been fully uploaded again. (s3FileCacheHoursAgo, allowS3ExistenceOptimization)

Ability to pause and resume downloads at will

Signing methods can respond to 401 and 403 response statuses and not trigger the automatic retry feature.

AWS Signature Version 2 and 4 (awsSignatureVersion)


Reduced memory footprint when calculating MD5 digests.

Parallel file uploads while respecting maxConcurrentParts.

If Evaporate reuses an interrupted upload or avoids uploading a file that is already available on S3, the new callback nameChanged will be invoked with the previous object name at the earliest moment. This indicates that requested object name was not used.


The progress() and complete() callbacks provide upload stats like transfer rate and time remaining.

Pause, Resume, Cancel can act on all in-progress file uploads

Cross Platform

  • Support for Node.js FileSystem (fs) ReadbleStreams. This means you can use Electron to upload a file directly from the file system's native File picker and avoid the usual browser restrictions.


$ npm install evaporate

API & Usage

The documentation for the usage of the whole API is available here.

This is a simple example of how you can configure it:

const Evaporate = require('EvaporateJS');
const Crypto = require('crypto');

const config = {
  signerUrl: SIGNER_URL,
  aws_key: AWS_KEY,
  bucket: AWS_BUCKET,
  cloudfront: true,
  computeContentMd5: true,
  cryptoMd5Method: data => Crypto

const uploadFile = evaporate => {
  const file = new File([""], "file_object_to_upload");

  const addConfig = {
    name: file.name,
    file: file,
    progress: progressValue => console.log('Progress', progressValue),
    complete: (_xhr, awsKey) => console.log('Complete!'),

    The bucket and some other properties
    can be changed per upload

  const overrides = {
    bucket: AWS_BUCKET_2

  evaporate.add(addConfig, overrides)
      awsObjectKey =>
        console.log('File successfully uploaded to:', awsObjectKey),
      reason =>
        console.log('File did not upload sucessfully:', reason);

return Evaporate.create(config).then(uploadFile);

More examples are available here.

Don't forget to check out the Browser Compatibility and Important Usage Notes pages for usage details.




Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

Download Details:

Author: TTLabs
Source Code: https://github.com/TTLabs/EvaporateJS 
License: BSD 3-Clause

#electron #javascript #browser #s3 

EvaporateJS: The Power of Browser to S3 Multipart Resumable Uploads
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