b2_finish_large_file

11 Sep 2026

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b2_finish_large_file

Updated on 11 Sep 2026

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/b2api/v4/b2_finish_large_file

Converts the parts that have been uploaded into a single B2 file

After you have uploaded the parts, use this call to combine the uploaded parts into one large file.

It may be that the call to finish a large file succeeds, but you don't know it because the request timed out, or the connection was broken. In that case, retrying will result in a 400 Bad Request response because the file is already finished. If that happens, we recommend calling b2_get_file_info to see if the file is there. If the file is there, you can count the upload as a success.

NOTE:

This API endpoint can be called using a GET request by converting the parameters in the request body to query parameters.

API Versions

v1: Application keys (July 26, 2018)

Incompatible change: After calling b2_authorize_account with an application key that does not have the right permissions, this call will return a 401 Unauthorized.

v1: Original release (September 22, 2015)

For information on all API versions, view our API changelog.

Header parameters

Authorization

stringRequired

An account authorization token, obtained from b2_authorize_account.

The token must have the writeFiles capability.

Body parameters

object

fileId

string Required

The ID returned by b2_start_large_file.

Example4_zb2f6f21365e1d29f6c580f18_f20150c1fda5f4c8d_d20180919_m215912_c002_v0001110_t0050

partSha1Array

Array of string Required

A JSON array of hex SHA1 checksums of the parts of the large file. This is a double-check that the right parts were uploaded in the right order, and that none were missed. Note that the part numbers start at 1, and the SHA1 of the part 1 is the first string in the array, at index 0.

["40d2b810f4b3978444b98d44a01cbc2680432726","956a86f77f2fd6181fcec963d3244689b720d845"]

Example[ "40d2b810f4b3978444b98d44a01cbc2680432726", "956a86f77f2fd6181fcec963d3244689b720d845" ]

string

Valid values[ "An SHA1 checksum" ]

Responses

200

The request succeeded.

The response headers include the Content-Type that was specified when the file was uploaded. They also include the X-Bz-FileName and X-Bz-Content-Sha1 headers, plus X-Bz-Info-* headers for any custom file info that was provided with the upload. The X-Bz-FileName uses percent-encoding, as if it were a URL parameter.

Expand All

object

accountId

string

The account that owns the file.

ExampleACCOUNT_ID

action

string

One of "start", "upload", "hide", "folder", or other values added in the future. "upload" means a file that was uploaded to B2 Cloud Storage. "start" means that a large file has been started, but not finished or canceled. "hide" means a file version marking the file as hidden, so that it will not show up in b2_list_file_names. "folder" is used to indicate a virtual folder when listing files.

Exampleupload

bucketId

string

The bucket that the file is in.

Examplee73ede9c9c8412db49f60715

contentLength

integer

The number of bytes stored in the file. Only useful when the action is "upload". Always 0 when the action is "start", "hide", or "folder".

Example208158542

contentSha1

string

The SHA1 of the bytes stored in the file as a 40-digit hex string. Large files do not have SHA1 checksums, and the value is "none". The value is null when the action is "hide" or "folder".

Examplenone

contentMd5

string

The MD5 of the bytes stored in the file as a 32-digit hex string. Not all files have an MD5 checksum, so this field is optional, and set to null for files that do not have one. Large files do not have MD5 checksums, and the value is null. The value is also null when the action is "hide" or "folder".

Example142be8357f26eda2ec6775cce257753b

contentType

string

When the action is "upload" or "start", the MIME type of the file, as specified when the file was uploaded. For "hide" action, always "application/x-bz-hide-marker". For "folder" action, always null.

Exampleb2/x-auto

fileId

string

The unique identifier for this version of this file. Used with b2_get_file_info, b2_download_file_by_id, and b2_delete_file_version. The value is null when for action "folder".

Example4_ze73ede9c9c8412db49f60715_f200b4e93fbae6252_d20150824_m224353_c900_v8881000_t0001

fileInfo

object

The custom information that was uploaded with the file. This is a JSON object, holding the name/value pairs that were uploaded with the file.

Example{ "author": "unknown" }

fileName

string

The name of this file, which can be used with b2_download_file_by_name.

Examplebigfile.dat

fileRetention

object

The Object Lock retention settings for this file, if any. This field is filtered based on application key capabilities; the readFileRetentions capability is required to access the value. See Object Lock for more details on response structure. This field is omitted when the action is "hide" or "folder".

Example{ "isClientAuthorizedToRead": true, "value": { "mode": null, "retainUntilTimestamp": null } }

isClientAuthorizedToRead

boolean

value

object

mode

string

retainUntilTimestamp

integer

legalHold

object

The Object Lock legal hold status for this file, if any. This field is filtered based on application key capabilities; the readFileLegalHolds capability is required to access the value. See Object Lock for more details on response structure. This field is omitted when the action is "hide" or "folder".

Example{ "isClientAuthorizedToRead": true, "value": null }

isClientAuthorizedToRead

boolean

value

string

replicationStatus

string

The Replication Status for this file, if any. This will show either PENDING, COMPLETED, FAILED, or REPLICA For details see Cloud Replication

This field is omitted when the file is not part of a replication rule.

ExamplePENDING

serverSideEncryption

object

When the file is encrypted with Server-Side Encryption, the mode ("SSE-B2" or "SSE-C") and algorithm used to encrypt the data. If the file is not encrypted with Server-Side Encryption, then both mode and algorithm will be null. This field is omitted when the action is "hide" or "folder".

Example{ "algorithm": null, "mode": null }

mode

string

algorithm

string

uploadTimestamp

integer

This is a UTC time when this file was uploaded. It is a base 10 number of milliseconds since midnight, January 1, 1970 UTC. This fits in a 64 bit integer such as the type "long" in the programming language Java. It is intended to be compatible with Java's time long. For example, it can be passed directly into the java call Date.setTime(long time). Always 0 when the action is "folder".

Example1460162909000

400

status	code	description
400	bad_bucket_id	The requested bucket ID does not match an existing bucket.
400	bad_request	The request had the wrong fields or illegal values. The message returned with the error will describe the problem.

object

status

integer

The numeric HTTP status code. Always matches the status in the HTTP response.

Example400

code

string

A single-identifier code that identifies the error.

Exampleinvalid_bucket_name

message

string

A human-readable message, in English, saying what went wrong.

Examplebucket name is too long

401

status	code	description
401	bad_auth_token	The auth token used is not valid. Call b2_authorize_account again to either get a new one, or an error message describing the problem.
401	expired_auth_token	The auth token used has expired. Call b2_authorize_account again to get a new one.
401	unauthorized	The auth token used is valid, but does not authorize this call with these parameters. The capabilities of an auth token are determined by the application key used with b2_authorize_account.

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