In order to make it faster and easier to upload larger objects, Amazon S3 has introduced the new multipart upload feature and S3Express fully supports this feature.

By specifying the flag -mul when uploading files with the command put, S3Express will break your files into chunks and upload them separately. You can instruct S3Express to upload a number of chunks in parallel using the flag -t. If the upload of one single chunk fails, you can simply restart the upload and S3Express will restart from the last successful chunk instead of having to re-upload the entire file. If you do not want to restart an unfinished multipart upload, use the command rmupl to remove the upload.
 

Note: S3Express will also automatically apply the correct MD5 value when uploading files using multipart uploads: many S3 tools are unable to do that.