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This article shows you how to connect to Azure Blob Storage by using the Azure Blob Storage client library for JavaScript. Once connected, use thedeveloper guides to learn how your code can operate on containers, blobs, and features of the Blob Storage service.

If you're looking to start with a complete example, see the client library quickstart forJavaScript orTypeScript.

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Prerequisites

Azure subscription -create one for free
Azure storage account -create a storage account
Node.js LTS
TypeScript, if applicable
For client (browser) applications, you needbundling tools.

Set up your project

This section walks you through preparing a project to work with the Azure Blob Storage client library for JavaScript.

Open a command prompt and navigate to your project folder. Change<project-directory> to your folder name:

cd <project-directory>

If you don't have apackage.json file already in your directory, initialize the project to create the file:

npm init -y

From your project directory, install packages for the Azure Blob Storage and Azure Identity client libraries using thenpm install oryarn add commands. The@azure/identity package is needed for passwordless connections to Azure services.

npm install @azure/storage-blob @azure/identity

npm install typescript @azure/storage-blob @azure/identity

Authorize access and connect to Blob Storage

To connect an app to Blob Storage, create an instance of theBlobServiceClient class. This object is your starting point to interact with data resources at the storage account level. You can use it to operate on the storage account and its containers. You can also use the service client to create container clients or blob clients, depending on the resource you need to work with.

To learn more about creating and managing client objects, including best practices, seeCreate and manage client objects that interact with data resources.

You can authorize aBlobServiceClient object by using a Microsoft Entra authorization token, an account access key, or a shared access signature (SAS). For optimal security, Microsoft recommends using Microsoft Entra ID with managed identities to authorize requests against blob data. For more information, seeAuthorize access to blobs using Microsoft Entra ID.

To authorize with Microsoft Entra ID, you need to use asecurity principal. Which type of security principal you need depends on where your app runs. Use the following table as a guide:

Where the app runs	Security principal	Guidance
Local machine (developing and testing)	Service principal	To learn how to register the app, set up a Microsoft Entra group, assign roles, and configure environment variables, seeAuthorize access using developer service principals
Local machine (developing and testing)	User identity	To learn how to set up a Microsoft Entra group, assign roles, and sign in to Azure, seeAuthorize access using developer credentials
Hosted in Azure	Managed identity	To learn how to enable managed identity and assign roles, seeAuthorize access from Azure-hosted apps using a managed identity
Hosted outside of Azure (for example, on-premises apps)	Service principal	To learn how to register the app, assign roles, and configure environment variables, seeAuthorize access from on-premises apps using an application service principal

Authorize access using DefaultAzureCredential

An easy and secure way to authorize access and connect to Blob Storage is to obtain an OAuth token by creating aDefaultAzureCredential instance. You can then use that credential to create aBlobServiceClient object.

The following example creates aBlobServiceClient object usingDefaultAzureCredential:

const accountName = "<account-name>";const accountURL = `https://${accountName}.blob.core.windows.net`;const blobServiceClient = new BlobServiceClient(  accountURL,  new DefaultAzureCredential());

This code example can be used for JavaScript or TypeScript projects.

To use a shared access signature (SAS) token, append the token to the account URL string separated by a? delimiter. Then, create aBlobServiceClient object with the URL.

const accountName = "<account-name>";const sasToken = "<sas-token>";const accountURL = `https://${accountName}.blob.core.windows.net?${sasToken}`;const blobServiceClient = new BlobServiceClient(accountURL);

This code example can be used for JavaScript or TypeScript projects.

To learn more about generating and managing SAS tokens, see the following articles:

Note

For scenarios where shared access signatures (SAS) are used, Microsoft recommends using a user delegation SAS. A user delegation SAS is secured with Microsoft Entra credentials instead of the account key.

To use a storage account shared key, provide the key as a string and initialize aBlobServiceClient object.

const credential = new StorageSharedKeyCredential(accountName, accountKey);const blobServiceClient = new BlobServiceClient(  `https://${accountName}.blob.core.windows.net`,  credential);

This code example can be used for JavaScript or TypeScript projects.

You can also create aBlobServiceClient object using a connection string.

const blobServiceClient = BlobServiceClient.fromConnectionString(connectionString);

For information about how to obtain account keys and best practice guidelines for properly managing and safeguarding your keys, seeManage storage account access keys.

Important

The account access key should be used with caution. If your account access key is lost or accidentally placed in an insecure location, your service may become vulnerable. Anyone who has the access key is able to authorize requests against the storage account, and effectively has access to all the data.DefaultAzureCredential provides enhanced security features and benefits and is the recommended approach for managing authorization to Azure services.

Build your app

As you build apps to work with data resources in Azure Blob Storage, your code primarily interacts with three resource types: storage accounts, containers, and blobs. To learn more about these resource types, how they relate to one another, and how apps interact with resources, seeUnderstand how apps interact with Blob Storage data resources.

The following guides show you how to access data and perform specific actions using the Azure Storage client library for #"storage-retry-policy-javascript" data-linktype="relative-path">Configure a retry policyImplement retry policies for client operations.Copy blobsCopy a blob from one location to another.Create a containerCreate blob containers.Create a user delegation SASCreate a user delegation SAS for a container or blob.Create and manage blob leasesEstablish and manage a lock on a blob.Create and manage container leasesEstablish and manage a lock on a container.Delete and restoreDelete blobs and restore soft-deleted blobs.Delete and restore containersDelete containers and restore soft-deleted containers.Download blobsDownload blobs by using strings, streams, and file paths.Find blobs using tagsSet and retrieve tags, and use tags to find blobs.List blobsList blobs in different ways.List containersList containers in an account and the various options available to customize a listing.Manage properties and metadata (blobs)Get and set properties and metadata for blobs.Manage properties and metadata (containers)Get and set properties and metadata for containers.Performance tuning for data transfersOptimize performance for data transfer operations.Set or change a blob's access tierSet or change the access tier for a block blob.Upload blobsLearn how to upload blobs by using strings, streams, file paths, and other methods.

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Get started with Azure Blob Storage and JavaScript or TypeScript

In this article

Prerequisites

Set up your project

Authorize access and connect to Blob Storage

Authorize access using DefaultAzureCredential

Build your app

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