@azure/storage-blob (TypeScript/JavaScript)

SDK for Azure Blob Storage operations — upload, download, list, and manage blobs and containers.

Installation

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

Current Version: 12.x

Node.js: >= 18.0.0

Environment Variables

AZURE_STORAGE_ACCOUNT_NAME=<account-name> AZURE_STORAGE_ACCOUNT_KEY=<account-key>

OR connection string

AZURE_STORAGE_CONNECTION_STRING=DefaultEndpointsProtocol=https;AccountName=...

Authentication

DefaultAzureCredential (Recommended)

import { BlobServiceClient } from "@azure/storage-blob"; import { DefaultAzureCredential } from "@azure/identity";

const accountName = process.env.AZURE_STORAGE_ACCOUNT_NAME!; const client = new BlobServiceClient( https://${accountName}.blob.core.windows.net, new DefaultAzureCredential() );

Connection String

import { BlobServiceClient } from "@azure/storage-blob";

const client = BlobServiceClient.fromConnectionString( process.env.AZURE_STORAGE_CONNECTION_STRING! );

StorageSharedKeyCredential (Node.js only)

import { BlobServiceClient, StorageSharedKeyCredential } from "@azure/storage-blob";

const accountName = process.env.AZURE_STORAGE_ACCOUNT_NAME!; const accountKey = process.env.AZURE_STORAGE_ACCOUNT_KEY!;

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

SAS Token

import { BlobServiceClient } from "@azure/storage-blob";

const accountName = process.env.AZURE_STORAGE_ACCOUNT_NAME!; const sasToken = process.env.AZURE_STORAGE_SAS_TOKEN!; // starts with "?"

const client = new BlobServiceClient( https://${accountName}.blob.core.windows.net${sasToken} );

Client Hierarchy

BlobServiceClient (account level) └── ContainerClient (container level) └── BlobClient (blob level) ├── BlockBlobClient (block blobs - most common) ├── AppendBlobClient (append-only blobs) └── PageBlobClient (page blobs - VHDs)

Container Operations

Create Container

const containerClient = client.getContainerClient("my-container"); await containerClient.create();

// Or create if not exists await containerClient.createIfNotExists();

List Containers

for await (const container of client.listContainers()) { console.log(container.name); }

// With prefix filter for await (const container of client.listContainers({ prefix: "logs-" })) { console.log(container.name); }

Delete Container

await containerClient.delete(); // Or delete if exists await containerClient.deleteIfExists();

Blob Operations

Upload Blob (Simple)

const containerClient = client.getContainerClient("my-container"); const blockBlobClient = containerClient.getBlockBlobClient("my-file.txt");

// Upload string await blockBlobClient.upload("Hello, World!", 13);

// Upload Buffer const buffer = Buffer.from("Hello, World!"); await blockBlobClient.upload(buffer, buffer.length);

Upload from File (Node.js only)

const blockBlobClient = containerClient.getBlockBlobClient("uploaded-file.txt"); await blockBlobClient.uploadFile("/path/to/local/file.txt");

Upload from Stream (Node.js only)

import * as fs from "fs";

const blockBlobClient = containerClient.getBlockBlobClient("streamed-file.txt"); const readStream = fs.createReadStream("/path/to/local/file.txt");

await blockBlobClient.uploadStream(readStream, 4 * 1024 * 1024, 5, { // bufferSize: 4MB, maxConcurrency: 5 onProgress: (progress) => console.log(Uploaded ${progress.loadedBytes} bytes), });

Upload from Browser

const blockBlobClient = containerClient.getBlockBlobClient("browser-upload.txt");

// From File input const fileInput = document.getElementById("fileInput") as HTMLInputElement; const file = fileInput.files![0]; await blockBlobClient.uploadData(file);

// From Blob/ArrayBuffer const arrayBuffer = new ArrayBuffer(1024); await blockBlobClient.uploadData(arrayBuffer);

Download Blob

const blobClient = containerClient.getBlobClient("my-file.txt"); const downloadResponse = await blobClient.download();

// Read as string (browser & Node.js) const downloaded = await streamToText(downloadResponse.readableStreamBody!);

async function streamToText(readable: NodeJS.ReadableStream): Promise<string> { const chunks: Buffer[] = []; for await (const chunk of readable) { chunks.push(Buffer.from(chunk)); } return Buffer.concat(chunks).toString("utf-8"); }

Download to File (Node.js only)

const blockBlobClient = containerClient.getBlockBlobClient("my-file.txt"); await blockBlobClient.downloadToFile("/path/to/local/destination.txt");

Download to Buffer (Node.js only)

const blockBlobClient = containerClient.getBlockBlobClient("my-file.txt"); const buffer = await blockBlobClient.downloadToBuffer(); console.log(buffer.toString());

List Blobs

// List all blobs for await (const blob of containerClient.listBlobsFlat()) { console.log(blob.name, blob.properties.contentLength); }

// List with prefix for await (const blob of containerClient.listBlobsFlat({ prefix: "logs/" })) { console.log(blob.name); }

// List by hierarchy (virtual directories) for await (const item of containerClient.listBlobsByHierarchy("/")) { if (item.kind === "prefix") { console.log(Directory: ${item.name}); } else { console.log(Blob: ${item.name}); } }

Delete Blob

const blobClient = containerClient.getBlobClient("my-file.txt"); await blobClient.delete();

// Delete if exists await blobClient.deleteIfExists();

// Delete with snapshots await blobClient.delete({ deleteSnapshots: "include" });

Copy Blob

const sourceBlobClient = containerClient.getBlobClient("source.txt"); const destBlobClient = containerClient.getBlobClient("destination.txt");

// Start copy operation const copyPoller = await destBlobClient.beginCopyFromURL(sourceBlobClient.url); await copyPoller.pollUntilDone();

Blob Properties & Metadata

Get Properties

const blobClient = containerClient.getBlobClient("my-file.txt"); const properties = await blobClient.getProperties();

console.log("Content-Type:", properties.contentType); console.log("Content-Length:", properties.contentLength); console.log("Last Modified:", properties.lastModified); console.log("ETag:", properties.etag);

Set Metadata

await blobClient.setMetadata({ author: "John Doe", category: "documents", });

Set HTTP Headers

await blobClient.setHTTPHeaders({ blobContentType: "text/plain", blobCacheControl: "max-age=3600", blobContentDisposition: "attachment; filename=download.txt", });

SAS Token Generation (Node.js only)

Generate Blob SAS

import { BlobSASPermissions, generateBlobSASQueryParameters, StorageSharedKeyCredential, } from "@azure/storage-blob";

const sharedKeyCredential = new StorageSharedKeyCredential(accountName, accountKey);

const sasToken = generateBlobSASQueryParameters( { containerName: "my-container", blobName: "my-file.txt", permissions: BlobSASPermissions.parse("r"), // read only startsOn: new Date(), expiresOn: new Date(Date.now() + 3600 * 1000), // 1 hour }, sharedKeyCredential ).toString();

const sasUrl = https://${accountName}.blob.core.windows.net/my-container/my-file.txt?${sasToken};

Generate Container SAS

import { ContainerSASPermissions, generateBlobSASQueryParameters } from "@azure/storage-blob";

const sasToken = generateBlobSASQueryParameters( { containerName: "my-container", permissions: ContainerSASPermissions.parse("racwdl"), // read, add, create, write, delete, list expiresOn: new Date(Date.now() + 24 * 3600 * 1000), // 24 hours }, sharedKeyCredential ).toString();

Generate Account SAS

import { AccountSASPermissions, AccountSASResourceTypes, AccountSASServices, generateAccountSASQueryParameters, } from "@azure/storage-blob";

const sasToken = generateAccountSASQueryParameters( { services: AccountSASServices.parse("b").toString(), // blob resourceTypes: AccountSASResourceTypes.parse("sco").toString(), // service, container, object permissions: AccountSASPermissions.parse("rwdlacupi"), // all permissions expiresOn: new Date(Date.now() + 24 * 3600 * 1000), }, sharedKeyCredential ).toString();

Blob Types

Block Blob (Default)

Most common type for text and binary files.

const blockBlobClient = containerClient.getBlockBlobClient("document.pdf"); await blockBlobClient.uploadFile("/path/to/document.pdf");

Append Blob

Optimized for append operations (logs, audit trails).

const appendBlobClient = containerClient.getAppendBlobClient("app.log");

// Create the append blob await appendBlobClient.create();

// Append data await appendBlobClient.appendBlock("Log entry 1\n", 12); await appendBlobClient.appendBlock("Log entry 2\n", 12);

Page Blob

Fixed-size blobs for random read/write (VHDs).

const pageBlobClient = containerClient.getPageBlobClient("disk.vhd");

// Create 512-byte aligned page blob await pageBlobClient.create(1024 * 1024); // 1MB

// Write pages (must be 512-byte aligned) const buffer = Buffer.alloc(512); await pageBlobClient.uploadPages(buffer, 0, 512);

Error Handling

import { RestError } from "@azure/storage-blob";

try { await containerClient.create(); } catch (error) { if (error instanceof RestError) { switch (error.statusCode) { case 404: console.log("Container not found"); break; case 409: console.log("Container already exists"); break; case 403: console.log("Access denied"); break; default: console.error(Storage error ${error.statusCode}: ${error.message}); } } throw error; }

TypeScript Types Reference

import { // Clients BlobServiceClient, ContainerClient, BlobClient, BlockBlobClient, AppendBlobClient, PageBlobClient,

// Authentication StorageSharedKeyCredential, AnonymousCredential,

// SAS BlobSASPermissions, ContainerSASPermissions, AccountSASPermissions, AccountSASServices, AccountSASResourceTypes, generateBlobSASQueryParameters, generateAccountSASQueryParameters,

// Options & Responses BlobDownloadResponseParsed, BlobUploadCommonResponse, ContainerCreateResponse, BlobItem, ContainerItem,

// Errors RestError, } from "@azure/storage-blob";

Best Practices

• Use DefaultAzureCredential — Prefer AAD over connection strings/keys

• Use streaming for large files — uploadStream /downloadToFile for files > 256MB

• Set appropriate content types — Use setHTTPHeaders for correct MIME types

• Use SAS tokens for client access — Generate short-lived tokens for browser uploads

• Handle errors gracefully — Check RestError.statusCode for specific handling

• Use *IfNotExists methods — For idempotent container/blob creation

• Close clients — Not required but good practice in long-running apps

Platform Differences

Feature Node.js Browser

StorageSharedKeyCredential

✅ ❌

uploadFile()

✅ ❌

uploadStream()

✅ ❌

downloadToFile()

✅ ❌

downloadToBuffer()

✅ ❌

uploadData()

✅ ✅

SAS generation ✅ ❌

DefaultAzureCredential ✅ ❌

Anonymous/SAS access ✅ ✅