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@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 ✅ ✅
When to Use This skill is applicable to execute the workflow or actions described in the overview.
Limitations
Use this skill only when the task clearly matches the scope described above.
Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.