Vercel blob

Vercel Blob (Object Storage)

Status: Production Ready Last Updated: 2025-12-14 Dependencies: None Latest Versions: @vercel/[email protected]

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Quick Start (3 Minutes)

1. Create & Configure

# In Vercel dashboard: Storage → Create Database → Blob
vercel env pull .env.local

Creates: BLOB_READ_WRITE_TOKEN

2. Install

bun add @vercel/blob

3. Upload File (Server Action)

'use server';

import { put } from '@vercel/blob';

export async function uploadFile(formData: FormData) {
  const file = formData.get('file') as File;

  const blob = await put(file.name, file, {
    access: 'public',
    contentType: file.type
  });

  return blob.url;
}

4. Basic Operations

import { put, del, list } from '@vercel/blob';

// Upload
const blob = await put('path/file.jpg', file, { access: 'public' });

// Delete
await del(blob.url);

// List with pagination
const { blobs, cursor } = await list({ prefix: 'uploads/', limit: 100 });

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Critical Rules

Always Do

Rule	Why
Use client upload tokens for client-side uploads	Never expose BLOB_READ_WRITE_TOKEN to client
Set contentType explicitly	Correct browser handling for PDFs, videos
Use access: 'public' for CDN caching	Private files bypass CDN
Validate file type and size before upload	Prevent invalid uploads
Use pathname organization	avatars/, uploads/, documents/
Delete old files when replacing	Manage storage costs

Never Do

Rule	Why
Expose BLOB_READ_WRITE_TOKEN to client	Security vulnerability
Upload files >500MB without multipart	Use createMultipartUpload API
Use generic filenames	Use ${Date.now()}-${name} or addRandomSuffix: true
Skip file validation	Always validate type/size
Store sensitive data unencrypted	Encrypt before upload
Forget to handle pagination	list() returns max 1000 files

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Known Issues Prevention

This skill prevents 10 documented issues:

#	Error	Quick Fix
1	BLOB_READ_WRITE_TOKEN not defined	Run vercel env pull .env.local
2	Client token exposed	Use handleUpload() for client uploads
3	File size exceeded (500MB)	Use multipart upload API
4	Wrong content-type	Set contentType: file.type
5	No CDN caching	Use access: 'public'
6	Missing files in list	Use cursor pagination
7	Delete fails silently	Use exact URL from put()
8	Upload timeout	Use client-side upload for large files
9	Filename collisions	Add timestamp or addRandomSuffix: true
10	State not updated	Use onUploadCompleted callback

See: references/known-issues.md for complete solutions with code examples.

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Common Patterns Summary

Pattern	Use Case	Key API
Avatar Upload	User profile images	put, del
Protected Upload	Private documents	put with access: 'private'
Image Gallery	List & paginate	list with cursor
Client Upload	Large files, progress	upload, handleUpload
Multipart Upload	Files >500MB	createMultipartUpload, uploadPart
Batch Operations	Multiple files	Promise.all, del([...])
Image Processing	Optimize before upload	sharp + put

See: references/common-patterns.md for complete implementations.

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Client-Side Upload (Essential Pattern)

Server Action (Token Generation):

'use server';

import { handleUpload, type HandleUploadBody } from '@vercel/blob/client';

export async function generateUploadToken(body: HandleUploadBody) {
  return await handleUpload({
    body,
    request: new Request('https://dummy'),
    onBeforeGenerateToken: async (pathname) => ({
      allowedContentTypes: ['image/jpeg', 'image/png', 'image/webp'],
      maximumSizeInBytes: 5 * 1024 * 1024
    }),
    onUploadCompleted: async ({ blob }) => {
      // Save to database
      await db.insert(uploads).values({ url: blob.url, pathname: blob.pathname });
    }
  });
}

Client Component:

'use client';

import { upload } from '@vercel/blob/client';

const blob = await upload(file.name, file, {
  access: 'public',
  handleUploadUrl: '/api/upload'
});

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Configuration

.env.local

# Created by: vercel env pull .env.local
BLOB_READ_WRITE_TOKEN="vercel_blob_rw_xxxxx"

.gitignore

.env.local
.env*.local

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When to Load References

Reference	Load When...
references/known-issues.md	Debugging upload errors, token issues, or CDN caching problems
references/common-patterns.md	Implementing avatar uploads, galleries, client uploads, or multipart uploads

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Dependencies

{
  "dependencies": {
    "@vercel/blob": "^2.0.0"
  }
}

Free Tier Limits: 100GB bandwidth/month, 500MB max file size

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Official Documentation

• Vercel Blob: https://vercel.com/docs/storage/vercel-blob
• Client Upload: https://vercel.com/docs/storage/vercel-blob/client-upload
• SDK Reference: https://vercel.com/docs/storage/vercel-blob/using-blob-sdk
• GitHub: https://github.com/vercel/storage

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Troubleshooting

Problem	Solution
BLOB_READ_WRITE_TOKEN not defined	Run vercel env pull .env.local
File size exceeded (>500MB)	Use multipart upload API
Client upload fails	Use handleUpload() server-side
Files not deleting	Use exact URL from put() response

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Token Savings: ~60% (patterns extracted to references) Error Prevention: 100% (all 10 documented issues) Ready for production!