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# Vercel Blob
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Vercel Blob is a comprehensive JavaScript API client for Vercel's cloud blob storage service, enabling developers to upload, download, list, and manage files in the cloud. It supports both server-side and client-side upload patterns, with server uploads limited to 4.5MB on Vercel and client uploads supporting files up to 5TB. The library offers a complete set of operations including put (upload), head (metadata), list (directory listing), copy, delete, and folder creation.
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## Package Information
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- **Package Name**: @vercel/blob
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- **Package Type**: npm
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- **Language**: TypeScript
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- **Installation**: `npm install @vercel/blob`
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## Core Imports
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**Server-side API (main export):**
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```typescript
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import { put, list, head, del, copy, createFolder } from '@vercel/blob';
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```
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**Client-side API:**
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```typescript
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import { put, upload, handleUpload, generateClientTokenFromReadWriteToken } from '@vercel/blob/client';
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```
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**Multipart uploads:**
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```typescript
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import { createMultipartUpload, uploadPart, completeMultipartUpload, createMultipartUploader } from '@vercel/blob';
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```
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**Error handling:**
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```typescript
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import { BlobError, BlobAccessError, BlobNotFoundError } from '@vercel/blob';
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```
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**Utility functions:**
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```typescript
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import { getDownloadUrl, bytes } from '@vercel/blob';
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```
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For CommonJS:
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```javascript
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const { put, list, head, del } = require('@vercel/blob');
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const { upload, handleUpload } = require('@vercel/blob/client');
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```
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## Basic Usage
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**Server-side upload:**
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```typescript
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import { put } from '@vercel/blob';
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// Upload a file from server
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const result = await put('documents/report.pdf', file, {
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  access: 'public',
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  addRandomSuffix: true,
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});
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console.log(result.url); // https://[store-id].public.blob.vercel-storage.com/documents/report-abc123.pdf
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```
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**Client-side upload:**
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```typescript
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import { upload } from '@vercel/blob/client';
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// Upload from browser/client
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const result = await upload('profile.jpg', file, {
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  access: 'public',
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  handleUploadUrl: '/api/upload', // Your server endpoint
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});
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console.log(result.url);
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```
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**List and manage blobs:**
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```typescript
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import { list, head, del } from '@vercel/blob';
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// List all blobs
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const { blobs } = await list();
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// Get metadata without downloading
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const metadata = await head('documents/report.pdf');
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console.log(metadata.size, metadata.uploadedAt);
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// Delete blobs
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await del(['old-file.txt', 'temp-data.json']);
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```
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## Architecture
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Vercel Blob is designed around several key concepts:
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- **Dual API Design**: Separate server-side and client-side APIs optimized for their respective environments
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- **Token-based Authentication**: Server tokens for backend operations, client tokens for frontend uploads
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- **Upload Patterns**: Simple uploads for small files, multipart uploads for large files up to 5TB
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- **Cross-platform Compatibility**: Works in Node.js, Edge Runtime, and browsers with automatic environment detection
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- **Type Safety**: Full TypeScript definitions with generic type preservation
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- **Error Handling**: Comprehensive error classes for different failure scenarios
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## Capabilities
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### Server-side Operations
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Core blob storage operations designed for server-side execution with full API access and higher upload limits.
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```typescript { .api }
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function put(pathname: string, body: PutBody, options: PutCommandOptions): Promise<PutBlobResult>;
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function del(urlOrPathname: string | string[], options?: BlobCommandOptions): Promise<void>;
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function head(urlOrPathname: string, options?: BlobCommandOptions): Promise<HeadBlobResult>;
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function list(options?: ListCommandOptions): Promise<ListBlobResult>;
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function copy(fromUrlOrPathname: string, toPathname: string, options: CopyCommandOptions): Promise<CopyBlobResult>;
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function createFolder(pathname: string, options?: BlobCommandOptions): Promise<CreateFolderResult>;
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```
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[Server-side API](./server-api.md)
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### Client-side Operations
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Upload operations designed for client-side execution with token-based security and support for large file uploads.
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```typescript { .api }
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function put(pathname: string, body: PutBody, options: ClientPutCommandOptions): Promise<PutBlobResult>;
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function upload(pathname: string, body: PutBody, options: UploadOptions): Promise<PutBlobResult>;
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function handleUpload(options: HandleUploadOptions): Promise<HandleUploadResult>;
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function generateClientTokenFromReadWriteToken(options: GenerateClientTokenOptions): Promise<string>;
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```
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[Client-side API](./client-api.md)
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### Multipart Uploads
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Large file upload system supporting files up to 5TB with parallel upload, retry logic, and progress tracking.
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```typescript { .api }
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function createMultipartUpload(pathname: string, options: CommonCreateBlobOptions): Promise<MultipartUploadInfo>;
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function uploadPart(pathname: string, body: PutBody, options: UploadPartCommandOptions): Promise<Part>;
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function completeMultipartUpload(pathname: string, parts: Part[], options: CompleteMultipartUploadCommandOptions): Promise<PutBlobResult>;
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function createMultipartUploader(pathname: string, options: CommonCreateBlobOptions): Promise<MultipartUploader>;
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```
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[Multipart Uploads](./multipart-uploads.md)
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### Utility Functions
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Helper functions for working with blob URLs and data processing.
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```typescript { .api }
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function getDownloadUrl(blobUrl: string): string;
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function bytes(val: string | number): number | null;
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```
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### Error Handling
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Comprehensive error system with specific error types for different failure scenarios and detailed error messages.
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```typescript { .api }
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class BlobError extends Error;
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class BlobAccessError extends BlobError;
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class BlobNotFoundError extends BlobError;
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class BlobStoreNotFoundError extends BlobError;
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class BlobStoreSuspendedError extends BlobError;
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```
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[Error Handling](./errors.md)
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## Common Types
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```typescript { .api }
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interface PutBlobResult {
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  url: string;
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  downloadUrl: string;
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  pathname: string;
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  contentType: string;
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  contentDisposition: string;
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}
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interface BlobCommandOptions {
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  token?: string;
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  abortSignal?: AbortSignal;
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}
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interface CommonCreateBlobOptions extends BlobCommandOptions {
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  access: 'public';
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  addRandomSuffix?: boolean;
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  allowOverwrite?: boolean;
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  contentType?: string;
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  cacheControlMaxAge?: number;
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}
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type PutBody = string | Readable | Buffer | Blob | ArrayBuffer | ReadableStream | File;
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interface UploadProgressEvent {
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  loaded: number;
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  total: number;
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  percentage: number;
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}
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type OnUploadProgressCallback = (progressEvent: UploadProgressEvent) => void;
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interface MultipartUploader {
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  key: string;
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  uploadId: string;
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  uploadPart(partNumber: number, body: PutBody): Promise<Part>;
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  complete(parts: Part[]): Promise<PutBlobResult>;
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}
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interface Part {
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  etag: string;
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  partNumber: number;
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}
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interface MultipartUploadInfo {
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  key: string;
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  uploadId: string;
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}
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interface HeadBlobResult {
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  size: number;
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  uploadedAt: Date;
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  pathname: string;
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  contentType: string;
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  contentDisposition: string;
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  url: string;
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  downloadUrl: string;
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  cacheControl: string;
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}
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interface ListBlobResult {
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  blobs: ListBlobResultBlob[];
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  cursor?: string;
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  hasMore: boolean;
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}
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interface ListBlobResultBlob {
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  url: string;
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  downloadUrl: string;
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  pathname: string;
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  size: number;
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  uploadedAt: Date;
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}
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interface CopyBlobResult {
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  url: string;
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  downloadUrl: string;
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  pathname: string;
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  contentType: string;
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  contentDisposition: string;
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}
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interface CreateFolderResult {
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  pathname: string;
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  url: string;
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}
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```
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## Environment Variables
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- **`BLOB_READ_WRITE_TOKEN`**: Primary token for server-side blob operations
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- **`VERCEL_BLOB_API_URL`**: Custom API URL (development only)
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- **`NEXT_PUBLIC_VERCEL_BLOB_API_URL`**: Public API URL for client-side operations