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Protocol

Version: 1.0.0 (SemVer)
Date: 2016-03-25
Authors: Felix Geisendörfer, Kevin van Zonneveld, Tim Koschützki, Naren Venkataraman, Marius Kleidl
Collaborators: Bruno de Carvalho, James Butler, Øystein Steimler, Sam Rijs, Khang Toh, Jacques Boscq, Jérémy FRERE, Pieter Hintjens, Stephan Seidt, Aran Wilkinson, Svein Ove Aas, Oliver Anan, Tim, j4james, Julian Reschke, Evert Pot, Jochen Kupperschmidt, Andrew Fenn, Kevin Swiber, Jan Kohlhof, eno, Luke Arduini, Jim Schmid, Jeffrey ‘jf’ Lim, Daniel Lopretto, Mark Murphy, Peter Darrow, Gargaj, Tomasz Rydzyński, Tino de Bruijn, Jonas mg, Christian Ulbrich, Jon Gjengset, Michael Elovskikh, Rick Olson, J. Ryan Stinnett, Ifedapo Olarewaju

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.

Status

Following SemVer, as of 1.0.0 tus is ready for general adoption. We don’t expect to make breaking changes, but if we do, those will have to be in a 2.0.0. Introducing a new extension or any backwards-compatible change adding new functionality will result in a bumped MINOR version.

Contributing

This protocol is authored and owned by the tus community. We welcome patches and feedback via GitHub. All authors and collaborators will be listed as such in the protocol header.

Please also let us know about any implementations (open source or commercial) if you’d like to be listed on the implementations page.

Abstract

The protocol provides a mechanism for resumable file uploads via HTTP/1.1 (RFC 7230) and HTTP/2 (RFC 7540).

Notation

Characters enclosed by square brackets indicate a placeholder (e.g. [size]).

The terms space, comma, and semicolon refer to their ASCII representations.

Core Protocol

The core protocol describes how to resume an interrupted upload. It assumes that you already have a URL for the upload, usually created via the Creation extension.

All Clients and Servers MUST implement the core protocol.

This specification does not describe the structure of URLs, as that is left for the specific implementation to decide. All URLs shown in this document are meant for example purposes only.

In addition, the implementation of authentication and authorization is left for the Server to decide.

Example

A HEAD request is used to determine the offset at which the upload should be continued.

The example below shows the continuation of a 100 byte upload that was interrupted after 70 bytes were transferred.

Request:

HEAD /files/24e533e02ec3bc40c387f1a0e460e216 HTTP/1.1
Host: tus.example.org
Tus-Resumable: 1.0.0

Response:

HTTP/1.1 200 OK
Upload-Offset: 70
Tus-Resumable: 1.0.0

Given the offset, the Client uses the PATCH method to resume the upload:

Request:

PATCH /files/24e533e02ec3bc40c387f1a0e460e216 HTTP/1.1
Host: tus.example.org
Content-Type: application/offset+octet-stream
Content-Length: 30
Upload-Offset: 70
Tus-Resumable: 1.0.0

[remaining 30 bytes]

Response:

HTTP/1.1 204 No Content
Tus-Resumable: 1.0.0
Upload-Offset: 100

Headers

Upload-Offset

The Upload-Offset request and response header indicates a byte offset within a resource. The value MUST be a non-negative integer.

Upload-Length

The Upload-Length request and response header indicates the size of the entire upload in bytes. The value MUST be a non-negative integer.

Tus-Version

The Tus-Version response header MUST be a comma-separated list of protocol versions supported by the Server. The list MUST be sorted by Server’s preference where the first one is the most preferred one.

Tus-Resumable

The Tus-Resumable header MUST be included in every request and response except for OPTIONS requests. The value MUST be the version of the protocol used by the Client or the Server.

If the the version specified by the Client is not supported by the Server, it MUST respond with the 412 Precondition Failed status and MUST include the Tus-Version header into the response. In addition, the Server MUST NOT process the request.

Tus-Extension

The Tus-Extension response header MUST be a comma-separated list of the extensions supported by the Server. If no extensions are supported, the Tus-Extension header MUST be omitted.

Tus-Max-Size

The Tus-Max-Size response header MUST be a non-negative integer indicating the maximum allowed size of an entire upload in bytes. The Server SHOULD set this header if there is a known hard limit.

X-HTTP-Method-Override

The X-HTTP-Method-Override request header MUST be a string which MUST be interpreted as the request’s method by the Server, if the header is presented. The actual method of the request MUST be ignored. The Client SHOULD use this header if its environment does not support the PATCH or DELETE methods.

Requests

The Server MUST always include the Upload-Offset header in the response for a HEAD request, even if the offset is 0, or the upload is already considered completed. If the size of the upload is known, the Server MUST include the Upload-Length header in the response. If the resource is not found, the Server SHOULD return either the 404 Not Found, 410 Gone or 403 Forbidden status without the Upload-Offset header.

The Server MUST prevent the client and/or proxies from caching the response by adding the Cache-Control: no-store header to the response.

PATCH

The Server SHOULD accept PATCH requests against any upload URL and apply the bytes contained in the message at the given offset specified by the Upload-Offset header. All PATCH requests MUST use Content-Type: application/offset+octet-stream.

The Upload-Offset header’s value MUST be equal to the current offset of the resource. In order to achieve parallel upload the Concatenation extension MAY be used. If the offsets do not match, the Server MUST respond with the 409 Conflict status without modifying the upload resource.

The Client SHOULD send all the remaining bytes of an upload in a single PATCH request, but MAY also use multiple small requests successively for scenarios where this is desirable. One example for these situations is when the Checksum extension is used.

The Server MUST acknowledge successful PATCH requests with the 204 No Content status. It MUST include the Upload-Offset header containing the new offset. The new offset MUST be the sum of the offset before the PATCH request and the number of bytes received and processed or stored during the current PATCH request.

Both, Client and Server, SHOULD attempt to detect and handle network errors predictably. They MAY do so by checking for read/write socket errors, as well as setting read/write timeouts. A timeout SHOULD be handled by closing the underlying connection.

The Server SHOULD always attempt to store as much of the received data as possible.

OPTIONS

An OPTIONS request MAY be used to gather information about the Server’s current configuration. A successful response indicated by the 204 No Content or 200 OK status MUST contain the Tus-Version header. It MAY include the Tus-Extension and Tus-Max-Size headers.

The Client SHOULD NOT include the Tus-Resumable header in the request and the Server MUST ignore the header.

Example

This example clarifies the response for an OPTIONS request. The version used in both, request and response, is 1.0.0 while the Server is also capable of handling 0.2.2 and 0.2.1. Uploads with a total size of up to 1GB are allowed and the extensions for Creation and Expiration are enabled.

Request:

OPTIONS /files HTTP/1.1
Host: tus.example.org

Response:

HTTP/1.1 204 No Content
Tus-Resumable: 1.0.0
Tus-Version: 1.0.0,0.2.2,0.2.1
Tus-Max-Size: 1073741824
Tus-Extension: creation,expiration

Protocol Extensions

Clients and Servers are encouraged to implement as many of the extensions as possible. Feature detection SHOULD be achieved by the Client sending an OPTIONS request and the Server responding with the Tus-Extension header.

Creation

The Client and the Server SHOULD implement the upload creation extension. If the Server supports this extension, it MUST add creation to the Tus-Extension header.

Example

An empty POST request is used to create a new upload resource. The Upload-Length header indicates the size of entire upload in bytes.

Request:

POST /files HTTP/1.1
Host: tus.example.org
Content-Length: 0
Upload-Length: 100
Tus-Resumable: 1.0.0
Upload-Metadata: filename d29ybGRfZG9taW5hdGlvbl9wbGFuLnBkZg==

Response:

HTTP/1.1 201 Created
Location: https://tus.example.org/files/24e533e02ec3bc40c387f1a0e460e216
Tus-Resumable: 1.0.0

The new resource has an implicit offset of 0 allowing the Client to use the core protocol for performing the actual upload.

Headers

Upload-Defer-Length

The Upload-Defer-Length request and response header indicates that the size of the upload is not known currently and will be transferred later. Its value MUST be 1. If the length of an upload is not deferred, this header MUST be omitted.

Upload-Metadata

The Upload-Metadata request and response header MUST consist of one or more comma-separated key-value pairs. The key and value MUST be separated by a space. The key MUST NOT contain spaces and commas and MUST NOT be empty. The key SHOULD be ASCII encoded and the value MUST be Base64 encoded. All keys MUST be unique.

Requests

POST

The Client MUST send a POST request against a known upload creation URL to request a new upload resource. The request MUST include one of the following headers:

a) Upload-Length to indicate the size of an entire upload in bytes.

b) Upload-Defer-Length: 1 if upload size is not known at the time. Once it is known the Client MUST set the Upload-Length header in the next PATCH request. Once set the length MUST NOT be changed. As long as the length of the upload is not known, the Server MUST set Upload-Defer-Length: 1 in all responses to HEAD requests.

If the Server supports deferring length, it MUST add creation-defer-length to the Tus-Extension header.

The Client MAY supply the Upload-Metadata header to add additional metadata to the upload creation request. The Server MAY decide to ignore or use this information to further process the request or to reject it. If an upload contains additional metadata, responses to HEAD requests MUST include the Upload-Metadata header and its value as specified by the Client during the creation.

If the length of the upload exceeds the maximum, which MAY be specified using the Tus-Max-Size header, the Server MUST respond with the 413 Request Entity Too Large status.

The Server MUST acknowledge a successful upload creation with the 201 Created status. The Server MUST set the Location header to the URL of the created resource. This URL MAY be absolute or relative.

The Client MUST perform the actual upload using the core protocol.

Expiration

The Server MAY remove unfinished uploads once they expire. In order to indicate this behavior to the Client, the Server MUST add expiration to the Tus-Extension header.

Example

The unfinished upload is available until the time specified in Upload-Expires. After this date the upload can not be resumed.

Request:

PATCH /files/24e533e02ec3bc40c387f1a0e460e216 HTTP/1.1
Host: tus.example.org
Content-Type: application/offset+octet-stream
Content-Length: 30
Upload-Offset: 70
Tus-Resumable: 1.0.0

[remaining 30 bytes]

Response:

HTTP/1.1 204 No Content
Upload-Expires: Wed, 25 Jun 2014 16:00:00 GMT
Tus-Resumable: 1.0.0
Upload-Offset: 100

Headers

Upload-Expires

The Upload-Expires response header indicates the time after which the unfinished upload expires. A Server MAY wish to remove incomplete uploads after a given period of time to prevent abandoned uploads from taking up extra storage. The Client SHOULD use this header to determine if an upload is still valid before attempting to the resume the upload.

This header MUST be included in every PATCH response if the upload is going to expire. If the expiration is known at the creation, the Upload-Expires header MUST be included in the response to the initial POST request. Its value MAY change over time.

If a Client does attempt to resume an upload which has since been removed by the Server, the Server SHOULD respond with the404 Not Found or 410 Gone status. The latter one SHOULD be used if the Server is keeping track of expired uploads. In both cases the Client SHOULD start a new upload.

The value of the Upload-Expires header MUST be in RFC 7231 datetime format.

Checksum

The Client and the Server MAY implement and use this extension to verify data integrity of each PATCH request. If supported, the Server MUST add checksum to the Tus-Extension header.

A Client MAY include the Upload-Checksum header in a PATCH request. Once the entire request has been received, the Server MUST verify the uploaded chunk against the provided checksum using the specified algorithm. Depending on the result the Server MAY respond with one of the following status code: 1) 400 Bad Request if the checksum algorithm is not supported by the server, 2) 460 Checksum Mismatch if the checksums mismatch or 3) 204 No Content if the checksums match and the processing of the data succeeded. In the first two cases the uploaded chunk MUST be discarded, and the upload and its offset MUST NOT be updated.

The Server MUST support at least the SHA1 checksum algorithm identified by sha1. The names of the checksum algorithms MUST only consist of ASCII characters with the modification that uppercase characters are excluded.

The Tus-Checksum-Algorithm header MUST be included in the response to an OPTIONS request.

If the hash cannot be calculated at the beginning of the upload, it MAY be included as a trailer. If the Server can handle trailers, this behavior MUST be announced by adding checksum-trailer to the Tus-Extension header. Trailers, also known as trailing headers, are headers which are sent after the request’s body has been transmitted already. Following RFC 7230 they MUST be announced using the Trailer header and are only allowed in chunked transfers.

Headers

Tus-Checksum-Algorithm

The Tus-Checksum-Algorithm response header MUST be a comma-separated list of the checksum algorithms supported by the server.

Upload-Checksum

The Upload-Checksum request header contains information about the checksum of the current body payload. The header MUST consist of the name of the used checksum algorithm and the Base64 encoded checksum separated by a space.

Example

Request:

OPTIONS /files HTTP/1.1
Host: tus.example.org
Tus-Resumable: 1.0.0

Response:

HTTP/1.1 204 No Content
Tus-Resumable: 1.0.0
Tus-Version: 1.0.0
Tus-Extension: checksum
Tus-Checksum-Algorithm: md5,sha1,crc32

Request:

PATCH /files/17f44dbe1c4bace0e18ab850cf2b3a83 HTTP/1.1
Content-Length: 11
Upload-Offset: 0
Tus-Resumable: 1.0.0
Upload-Checksum: sha1 Kq5sNclPz7QV2+lfQIuc6R7oRu0=

hello world

Response:

HTTP/1.1 204 No Content
Tus-Resumable: 1.0.0
Upload-Offset: 11

Termination

This extension defines a way for the Client to terminate completed and unfinished uploads allowing the Server to free up used resources.

If this extension is supported by the Server, it MUST be announced by adding termination to the Tus-Extension header.

Requests

DELETE

When receiving a DELETE request for an existing upload the Server SHOULD free associated resources and MUST respond with the 204 No Content status confirming that the upload was terminated. For all future requests to this URL the Server SHOULD respond with the 404 Not Found or 410 Gone status.

Example

Request:

DELETE /files/24e533e02ec3bc40c387f1a0e460e216 HTTP/1.1
Host: tus.example.org
Content-Length: 0
Tus-Resumable: 1.0.0

Response:

HTTP/1.1 204 No Content
Tus-Resumable: 1.0.0

Concatenation

This extension can be used to concatenate multiple uploads into a single one enabling Clients to perform parallel uploads and to upload non-contiguous chunks. If the Server supports this extension, it MUST add concatenation to the Tus-Extension header.

A partial upload represents a chunk of a file. It is constructed by including the Upload-Concat: partial header while creating a new upload using the Creation extension. Multiple partial uploads are concatenated into a final upload in the specified order. The Server SHOULD NOT process these partial uploads until they are concatenated to form a final upload. The length of the final upload MUST be the sum of the length of all partial uploads.

In order to create a new final upload the Client MUST add the Upload-Concat header to the upload creation request. The value MUST be final followed by a semicolon and a space-separated list of the partial upload URLs that need to be concatenated. The partial uploads MUST be concatenated as per the order specified in the list. This concatenation request SHOULD happen after all of the corresponding partial uploads are completed. The Client MUST NOT include the Upload-Length header in the final upload creation.

The Client MAY send the concatenation request while the partial uploads are still in progress. This feature MUST be explicitly announced by the Server by adding concatenation-unfinished to the Tus-Extension header.

When creating a new final upload the partial uploads’ metadata SHALL NOT be transferred to the new final upload. All metadata SHOULD be included in the concatenation request using the Upload-Metadata header.

The Server MAY delete partial uploads after concatenation. They MAY however be used multiple times to form a final resource.

The Server MUST respond with the 403 Forbidden status to PATCH requests against a final upload URL and MUST NOT modify the final or its partial uploads.

The response to a HEAD request for a final upload SHOULD NOT contain the Upload-Offset header unless the concatenation has been successfully finished. After successful concatenation, the Upload-Offset and Upload-Length MUST be set and their values MUST be equal. The value of the Upload-Offset header before concatenation is not defined for a final upload.

The response to a HEAD request for a partial upload MUST contain the Upload-Offset header.

The Upload-Length header MUST be included if the length of the final resource can be calculated at the time of the request. Response to HEAD request against partial or final upload MUST include the Upload-Concat header and its value as received in the upload creation request.

Headers

Upload-Concat

The Upload-Concat request and response header MUST be set in both partial and final upload creation requests. It indicates whether the upload is either a partial or final upload. If the upload is a partial one, the header value MUST be partial. In the case of a final upload, its value MUST be final followed by a semicolon and a space-separated list of partial upload URLs that will be concatenated. The partial uploads URLs MAY be absolute or relative and MUST NOT contain spaces as defined in RFC 3986.

Example

In the following example the Host and Tus-Resumable headers are omitted for readability although they are required by the specification. In the beginning two partial uploads are created:

POST /files HTTP/1.1
Upload-Concat: partial
Upload-Length: 5

HTTP/1.1 201 Created
Location: https://tus.example.org/files/a
POST /files HTTP/1.1
Upload-Concat: partial
Upload-Length: 6

HTTP/1.1 201 Created
Location: https://tus.example.org/files/b

You are now able to upload data to the two partial resources using PATCH requests:

PATCH /files/a HTTP/1.1
Upload-Offset: 0
Content-Length: 5

hello

HTTP/1.1 204 No Content
PATCH /files/b HTTP/1.1
Upload-Offset: 0
Content-Length: 6

 world

HTTP/1.1 204 No Content

In the first request the string hello was uploaded while the second file now contains ` world` with a leading space.

The next step is to create the final upload consisting of the two earlier generated partial uploads. In following request no Upload-Length header is presented.

POST /files HTTP/1.1
Upload-Concat: final;/files/a /files/b

HTTP/1.1 201 Created
Location: https://tus.example.org/files/ab

The length of the final resource is now 11 bytes consisting of the string hello world.

HEAD /files/ab HTTP/1.1

HTTP/1.1 200 OK
Upload-Length: 11
Upload-Concat: final;/files/a /files/b

FAQ

Why is the protocol using custom headers?

We have carefully investigated the use of existing headers such as Range and Content-Range, but unfortunately they are defined in a way that makes them unsuitable for resumable file uploads.

We also considered using existing PATCH payload formats such as multipart/byteranges, but unfortunately the XHR2 FormData interface does not support custom headers for multipart parts, and the send() method does not allow streaming arbitrary data without loading all of it into memory.

That being said, custom headers also allowed us to greatly simplify the Client and Server implementations, so we’re quite happy with them.

Why are you not using the “X-“ prefix for your headers?

The “X-“ prefix for headers has been deprecated, see RFC 6648.

How can I deal with bad HTTP proxies?

If you are dealing with HTTP proxies that strip/modify HTTP headers or can’t handle PATCH requests properly, you should consider using HTTPS which will make it impossible for proxies to modify your requests and use the X-HTTP-Method-Override header which allows you to use POST requests.

If that is not an option for you, please reach out to us, we are open to defining a compatibility protocol extension.

How are pause/resume handled? When should I delete partial uploads?

The tus protocol is built upon the principles of simple pausing and resuming. In order to pause an upload you are allowed to end the current open request. The Server will store the uploaded data as long as no violations against other constraints (e.g. checksums) or internal errors occur. Once you are ready to resume an upload, send a HEAD request to the corresponding upload URL in order to obtain the available offset. After receiving a valid response you can upload more data using PATCH requests. You should keep in mind that the Server may delete an unfinished upload if it is not continued for a longer time period (see Expiration extension).

Before deleting an outstanding upload the Server should give the Client enough time to resolve potential networking issues. Since this duration depends heavily on the underlying application model, the protocol does not contain a specific number, but we recommend one week for a general use case.

License

Licensed under the MIT license, see LICENSE.txt.

Copyright (c) 2013-2016 Transloadit Ltd and Contributors.

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