TUS - Open Protocol for Resumable File Uploads

Introduction

Tus is a new open protocol for resumable uploads built on HTTP. It offers simple, cheap and reusable stacks for clients and servers. It supports any language, any platform and any network.

There are many freely available client and server implements. An demo is running at https://tus.io/demo.

Tus is a low-level building block, there's no one right way to do deploy resumable file uploads with it.

When should use tus?

• app running on partly unreliable networks.
• handle large files, avoid reupload.
• want to provide your users with the ability to pause & resume.
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How to get started

You'll need:

• server implementation (like: tusd).
• client implementation (like: tus-js-client for browsers and Node.js, or Uppy).

Protocol

A tus upload composed of different HTTP requests, each one has it's own purpose:

• POST

  First, client sends a POST request to the server to initiate the upload.
  This request tells the server basic information such as size or additional metadata.
  If the server accepts, will return a successful response with the Location header set to the upload URL.
  This upload URL is used to uniquely identify and reference the newly-created upload resource.
  For example:
  

• PATCH

  One the upload has been created, the client can start to transmit the actual upload content by send a PATCH request to the upload URL (returned in the previous POST request).
  The PATCH request sholud contain as much upload content as possible to minimize the upload duration. Also must contain the Upload-Offset header (tells the server at which byte offset the server should write the uploaded data).
  Your upload will be done when PATCH request successfully transfers the entirety of the upload contnet.

• HEAD

  If PATCH interrupted or failed, if the client attempt to resume, the client must know how much data the server has received.
  Therefore, HEAD rquest sent to the upload URL, client inspecting the returned Upload-Offset header. The client will send another PATCH request until the upload is completely done.
  

• DELETE

  A DELETE request can be sent to the upload URL to delete an upload. Ater this, the upload can be cleaned up by the server, resuming the upload is not possible anymore.

Concepts

• Upload-Offset: indicates a byte offset whitin a resource. (The simple way is to consider as a completely uploaded byte length, identifies the starting position of the data that has been received by the server.)
• Upload-Length: indicates the size of the entire upload in bytes.
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