---
name: azure-storage-blob-ts
description: |
Azure Blob Storage JavaScript/TypeScript SDK (@azure/storage-blob) for blob operations. Use for uploading, downloading, listing, and managing blobs and containers. Supports block blobs, append blobs, page blobs, SAS tokens, and streaming. Triggers: "blob storage", "@azure/storage-blob", "BlobServiceClient", "ContainerClient", "upload blob", "download blob", "SAS token", "block blob".
license: MIT
metadata:
author: Microsoft
version: "1.0.0"
package: '@azure/storage-blob'
---
# @azure/storage-blob (TypeScript/JavaScript)
SDK for Azure Blob Storage operations — upload, download, list, and manage blobs and containers.
## Installation
```bash
npm install @azure/storage-blob @azure/identity
```
**Current Version**: 12.x
**Node.js**: >= 18.0.0
## Environment Variables
```bash
AZURE_STORAGE_ACCOUNT_NAME=<account-name>
AZURE_STORAGE_ACCOUNT_KEY=<account-key>
# OR connection string
AZURE_STORAGE_CONNECTION_STRING=DefaultEndpointsProtocol=https;AccountName=...
AZURE_TOKEN_CREDENTIALS=prod # Required only if DefaultAzureCredential is used in production
```
## Authentication
### Microsoft Entra Token Credential (Recommended)
```typescript
import { BlobServiceClient } from "@azure/storage-blob";
import { DefaultAzureCredential, ManagedIdentityCredential } from "@azure/identity";
// Local dev: DefaultAzureCredential. Production: set AZURE_TOKEN_CREDENTIALS=prod or AZURE_TOKEN_CREDENTIALS=<specific_credential>
const credential = new DefaultAzureCredential({requiredEnvVars: ["AZURE_TOKEN_CREDENTIALS"]});
// Or use a specific credential directly in production:
// See https://learn.microsoft.com/javascript/api/overview/azure/identity-readme?view=azure-node-latest#credential-classes
// const credential = new ManagedIdentityCredential();
const accountName = process.env.AZURE_STORAGE_ACCOUNT_NAME!;
const client = new BlobServiceClient(
`https://${accountName}.blob.core.windows.net`,
credential
);
```
### Connection String
```typescript
import { BlobServiceClient } from "@azure/storage-blob";
const client = BlobServiceClient.fromConnectionString(
process.env.AZURE_STORAGE_CONNECTION_STRING!
);
```
### StorageSharedKeyCredential (Node.js only)
```typescript
import { BlobServiceClient, StorageSharedKeyCredential } from "@azure/storage-blob";
const accountName = process.env.AZURE_STORAGE_ACCOUNT_NAME!;
const accountKey = process.env.AZURE_STORAGE_ACCOUNT_KEY!;
const sharedKeyCredential = new StorageSharedKeyCredential(accountName, accountKey);
const client = new BlobServiceClient(
`https://${accountName}.blob.core.windows.net`,
sharedKeyCredential
);
```
### SAS Token
```typescript
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
```typescript
const containerClient = client.getContainerClient("my-container");
await containerClient.create();
// Or create if not exists
await containerClient.createIfNotExists();
```
### List Containers
```typescript
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
```typescript
await containerClient.delete();
// Or delete if exists
await containerClient.deleteIfExists();
```
## Blob Operations
### Upload Blob (Simple)
```typescript
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)
```typescript
const blockBlobClient = containerClient.getBlockBlobClient("uploaded-file.txt");
await blockBlobClient.uploadFile("/path/to/local/file.txt");
```
### Upload from Stream (Node.js only)
```typescript
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
```typescript
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
```typescript
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)
```typescript
const blockBlobClient = containerClient.getBlockBlobClient("my-file.txt");
await blockBlobClient.downloadToFile("/path/to/local/destination.txt");
```
### Download to Buffer (Node.js only)
```typescript
const blockBlobClient = containerClient.getBlockBlobClient("my-file.txt");
const buffer = await blockBlobClient.downloadToBuffer();
console.log(buffer.toString());
```
### List Blobs
```typescript
// 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: ${item.name}`);
}
}
```
### Delete Blob
```typescript
const blobClient = containerClient.getBlobClient("my-file.txt");
await blobClient.delete();
// Delete if exists
await blobClient.deleteIfExists();
// Delete with snapshots
await blobClient.delete({ deleteSnapshots: "include" });
```
### Copy Blob
```typescript
const sourceBlobClient = containerClient.getBlobClient("source.txt");
const destBlobClient = containerClient.getBlobClient("destination.txt");
// Start copy operation
const copyPoller = await destBlobClient.beginCopyFromURL(sourceBlobClient.url);
await copyPoller.pollUntilDone();
```
## Blob Properties & Metadata
### Get Properties
```typescript
const blobClient = containerClient.getBlobClient("my-file.txt");
const properties = await blobClient.getProperties();
console.log("Content-Type:", properties.contentType);
console.log("Content-Length:", properties.contentLength);
console.log("Last Modified:", properties.lastModified);
console.log("ETag:", properties.etag);
```
### Set Metadata
```typescript
await blobClient.setMetadata({
author: "John Doe",
category: "documents",
});
```
### Set HTTP Headers
```typescript
await blobClient.setHTTPHeaders({
blobContentType: "text/plain",
blobCacheControl: "max-age=3600",
blobContentDisposition: "attachment; filename=download.txt",
});
```
## SAS Token Generation (Node.js only)
### Generate Blob SAS
```typescript
import {
BlobSASPermissions,
generateBlobSASQueryParameters,
StorageSharedKeyCredential,
} from "@azure/storage-blob";
const sharedKeyCredential = new StorageSharedKeyCredential(accountName, accountKey);
const sasToken = generateBlobSASQueryParameters(
{
containerName: "my-container",
blobName: "my-file.txt",
permissions: BlobSASPermissions.parse("r"), // read only
startsOn: new Date(),
expiresOn: new Date(Date.now() + 3600 * 1000), // 1 hour
},
sharedKeyCredential
).toString();
const sasUrl = `https://${accountName}.blob.core.windows.net/my-container/my-file.txt?${sasToken}`;
```
### Generate Container SAS
```typescript
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
```typescript
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.
```typescript
const blockBlobClient = containerClient.getBlockBlobClient("document.pdf");
await blockBlobClient.uploadFile("/path/to/document.pdf");
```
### Append Blob
Optimized for append operations (logs, audit trails).
```typescript
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).
```typescript
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
```typescript
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
```typescript
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
1. **Use `DefaultAzureCredential` for local development; use `ManagedIdentityCredential` or `WorkloadIdentityCredential` for production**
2. **Use streaming for large files** — `uploadStream`/`downloadToFile` for files > 256MB
3. **Set appropriate content types** — Use `setHTTPHeaders` for correct MIME types
4. **Use SAS tokens for client access** — Generate short-lived tokens for browser uploads
5. **Handle errors gracefully** — Check `RestError.statusCode` for specific handling
6. **Use `*IfNotExists` methods** — For idempotent container/blob creation
7. **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 | ✅ | ✅ |