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Node.js Library for the Backblaze B2 Storage Service

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Backblaze B2 Node.js Library

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A customizable B2 client for Node.js:

  • Uses axios. You can control the axios instance at the request level (see
    config arguments) and at the global level (see
    config argument at instantiation) so you can use any axios feature.
  • Automatically retries on request failure. You can control retry behaviour using the
    argument at instantiation.


This library uses promises, so all actions on a

instance return a promise in the following pattern:
b2.instanceFunction(arg1, arg2).then(
    successFn(response) { ... },
    errorFn(err) { ... }

Basic Example

const B2 = require('backblaze-b2');

const b2 = new B2({ applicationKeyId: 'applicationKeyId', // or accountId: 'accountId' applicationKey: 'applicationKey' // or masterApplicationKey });

async function GetBucket() { try { await b2.authorize(); // must authorize first (authorization lasts 24 hrs) let response = await b2.getBucket({ bucketName: 'my-bucket' }); console.log(; } catch (err) { console.log('Error getting bucket:', err); } }

Response Object

Each request returns an object with:

  • status
    - int, html error Status
  • statusText
  • headers
  • config
  • request
  • data
    - actual returned data from backblaze,

How it works

Each action (see reference below) takes arguments and constructs an axios request. You can add additional axios options at the request level using:

  • The
    argument (object): each property in this object is added to the axios request object only if it does not conflict with an existing property.
  • The
    argument (object): each property in this object is added to the axios request object by overriding conflicting properties, if any. Don't use this unless you know what you're doing!
  • Both
    work by recursively merging properties, so if you pass
    axios: { headers: { 'your-custom-header': 'header-value' } }
    , the entire headers object will not be overridden - each header property (
    ) will be compared.


const B2 = require('backblaze-b2');

// All functions on the b2 instance return the response from the B2 API in the success callback // i.e. => {})

// create B2 object instance const b2 = new B2({ applicationKeyId: 'applicationKeyId', // or accountId: 'accountId' applicationKey: 'applicationKey', // or masterApplicationKey // optional: axios: { // overrides the axios instance default config, see }, retry: { retries: 3 // this is the default // for additional options, see } });

// common arguments - you can use these in any of the functions below const common_args = { // axios request level config, see axios: { timeout: 30000 // (example) }, axiosOverride: { /* Don't use me unless you know what you're doing! */ } }

// authorize with provided credentials (authorization expires after 24 hours) b2.authorize({ // ...common arguments (optional) }); // returns promise

// create bucket b2.createBucket({ bucketName: 'bucketName', bucketType: 'bucketType' // one of allPublic, allPrivate // ...common arguments (optional) }); // returns promise

// delete bucket b2.deleteBucket({ bucketId: 'bucketId' // ...common arguments (optional) }); // returns promise

// list buckets b2.listBuckets({ // ...common arguments (optional) }); // returns promise

// get the bucket b2.getBucket({ bucketName: 'bucketName', bucketId: 'bucketId' // optional // ...common arguments (optional) }); // returns promise

// update bucket b2.updateBucket({ bucketId: 'bucketId', bucketType: 'bucketType' // ...common arguments (optional) }); // returns promise

// get upload url b2.getUploadUrl({ bucketId: 'bucketId' // ...common arguments (optional) }); // returns promise

// upload file b2.uploadFile({ uploadUrl: 'uploadUrl', uploadAuthToken: 'uploadAuthToken', fileName: 'fileName', contentLength: 0, // optional data length, will default to data.byteLength or data.length if not provided mime: '', // optional mime type, will default to 'b2/x-auto' if not provided data: 'data', // this is expecting a Buffer, not an encoded string hash: 'sha1-hash', // optional data hash, will use sha1(data) if not provided info: { // optional info headers, prepended with X-Bz-Info- when sent, throws error if more than 10 keys set // valid characters should be a-z, A-Z and '-', all other characters will cause an error to be thrown key1: 'value', key2: 'value' }, onUploadProgress: (event) => {} || null // progress monitoring // ...common arguments (optional) }); // returns promise

// list file names b2.listFileNames({ bucketId: 'bucketId', startFileName: 'startFileName', maxFileCount: 100, delimiter: '', prefix: '' // ...common arguments (optional) }); // returns promise

// list file versions b2.listFileVersions({ bucketId: 'bucketId', startFileName: 'startFileName', startFileId: 'startFileId', maxFileCount: 100 // ...common arguments (optional) }); // returns promise

// list uploaded parts for a large file b2.listParts({ fileId: 'fileId', startPartNumber: 0, // optional maxPartCount: 100, // optional (max: 1000) // ...common arguments (optional) }); // returns promise

// hide file b2.hideFile({ bucketId: 'bucketId', fileName: 'fileName' // ...common arguments (optional) }); // returns promise

// get file info b2.getFileInfo({ fileId: 'fileId' // ...common arguments (optional) }); // returns promise

// get download authorization b2.getDownloadAuthorization({ bucketId: 'bucketId', fileNamePrefix: 'fileNamePrefix', validDurationInSeconds: 'validDurationInSeconds', // a number from 0 to 604800 b2ContentDisposition: 'b2ContentDisposition' // ...common arguments (optional) }); // returns promise

// download file by name b2.downloadFileByName({ bucketName: 'bucketName', fileName: 'fileName', responseType: 'arraybuffer', // options are as in axios: 'arraybuffer', 'blob', 'document', 'json', 'text', 'stream' onDownloadProgress: (event) => {} || null // progress monitoring // ...common arguments (optional) }); // returns promise

// download file by fileId b2.downloadFileById({ fileId: 'fileId', responseType: 'arraybuffer', // options are as in axios: 'arraybuffer', 'blob', 'document', 'json', 'text', 'stream' onDownloadProgress: (event) => {} || null // progress monitoring // ...common arguments (optional) }); // returns promise

// delete file version b2.deleteFileVersion({ fileId: 'fileId', fileName: 'fileName' // ...common arguments (optional) }); // returns promise

// start large file b2.startLargeFile({ bucketId: 'bucketId', fileName: 'fileName' // ...common arguments (optional) }); // returns promise

// get upload part url b2.getUploadPartUrl({ fileId: 'fileId' // ...common arguments (optional) }); // returns promise

// get upload part b2.uploadPart({ partNumber: 'partNumber', // A number from 1 to 10000 uploadUrl: 'uploadUrl', uploadAuthToken: 'uploadAuthToken', // comes from getUploadPartUrl(); data: Buffer // this is expecting a Buffer not an encoded string, hash: 'sha1-hash', // optional data hash, will use sha1(data) if not provided onUploadProgress: (event) => {} || null, // progress monitoring contentLength: 0, // optional data length, will default to data.byteLength or data.length if not provided // ...common arguments (optional) }); // returns promise

// finish large file b2.finishLargeFile({ fileId: 'fileId', partSha1Array: [partSha1Array] // array of sha1 for each part // ...common arguments (optional) }); // returns promise

// cancel large file b2.cancelLargeFile({ fileId: 'fileId' // ...common arguments (optional) }); // returns promise

// create key b2.createKey({ capabilities: [ 'readFiles', // option 1 b2.KEY_CAPABILITIES.READ_FILES, // option 2 // see for full list ], keyName: 'my-key-1', // letters, numbers, and '-' only, <=100 chars validDurationInSeconds: 3600, // expire after duration (optional) bucketId: 'bucketId', // restrict access to bucket (optional) namePrefix: 'prefix_', // restrict access to file prefix (optional) // ...common arguments (optional) }); // returns promise

// delete key b2.deleteKey({ applicationKeyId: 'applicationKeyId', // ...common arguments (optional) }); // returns promise

// list keys b2.listKeys({ maxKeyCount: 10, // limit number of keys returned (optional) startApplicationKeyId: '...', // use nextApplicationKeyId from previous response when maxKeyCount is set (optional) // ...common arguments (optional) }); // returns promise

Uploading Large Files Example

To upload large files, you should split the file into parts (between 5MB and 5GB) and upload each part seperately.

First, you initiate the large file upload to get the fileId:

let response = await b2.startLargeFile({ bucketId, fileName });
let fileId =;

Then, to upload parts, you request at least one

and use the response to upload the part with
. The url and token returned by
are valid for 24 hours or until
fails, in which case you should request another
to continue. You may utilize multiple
s in parallel to achieve greater upload throughput.

If you are unsure whether you should use multipart upload, refer to the

value returned by a call to
let response = await b2.getUploadPartUrl({ fileId });

let uploadURL =; let authToken =;

response = await b2.uploadPart({ partNumber: parNum, uploadUrl: uploadURL, uploadAuthToken: authToken, data: buf }); // status checks etc.

Then finish the uploadUrl:

let response = await b2.finishLargeFile({
    partSha1Array: => sha1(buf))

If an upload is interrupted, the fileId can be used to get a list of parts which have already been transmitted. You can then send the remaining parts before finally calling

let response = await b2.listParts({
    startPartNumber: 0,
    maxPartCount: 1000


See the CHANGELOG for a history of updates.

Upgrading from 0.9.x to 1.0.x

For this update, we've switched the back end HTTP request library from

as it has better Promise and progress support built in. However, there are a couple changes that will break your code and ruin your day. Here are the changes:
  • The Promise resolution has a different data structure. Where previously, the request response data was the root object in the promise resolution (
    ), this data now resides in
  • In v0.9.12, we added request progress reporting via the third parameter to
    . Because we are no longer using the same promise library, this functionality has been removed. However, progress reporting is still available by passing a callback function into the
    that you're calling. See the documentation below for details.
  • In v0.9.x,
    accepted a
    parameter as a String or Number. As of 1.0.0, the first parameter is now expected to be a plain Object of arguments.


Contributions, suggestions, and questions are welcome. Please review the contributing guidelines for details.

Authors and Contributors

  • Yakov Khalinsky (@yakovkhalinsky)
  • Ivan Kalinin (@IvanKalinin) at Isolary
  • Brandon Patton (@crazyscience) at Isolary
  • C. Bess (@cbess)
  • Amit (@Amit-A)
  • Zsombor Paróczi (@realhidden)
  • Oden (@odensc)

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