v0
storage
Vercel Blob Upload Failing with Size or Type Errors
File uploads to Vercel Blob Storage are failing in your v0-generated application. Users see generic error messages when trying to upload images, documents, or other files. The upload either times out, returns a 413 error, or fails silently with no file stored.
Vercel Blob has specific requirements around request body size, content types, and authentication tokens that v0 may not have configured correctly. The default Vercel serverless function body size limit of 4.5MB is often insufficient for image uploads.
Additionally, client-side upload implementations may fail due to CORS configuration issues or missing the BLOB_READ_WRITE_TOKEN environment variable in the correct scope.
Error Messages You Might See
BlobAccessError: Invalid token
Payload Too Large (413)
BlobUploadError: Failed to upload file
Failed to fetch blob upload URL
CORS error: Access-Control-Allow-Origin missing
Common Causes
- Body size limit exceeded — Vercel serverless functions have a 4.5MB body limit; large files need client-side upload
- Missing BLOB_READ_WRITE_TOKEN — environment variable not set or not available in the correct Vercel environment
- Wrong upload method — using server-side put() instead of client-side upload() for large files
- Content type not set — missing contentType option causes Blob to reject or misidentify the file
- CORS not configured — client-side uploads blocked by browser CORS policy
How to Fix It
- Use client-side uploads for large files — implement
upload()from @vercel/blob/client with a server-side token generation route - Set BLOB_READ_WRITE_TOKEN — add the token from Vercel Dashboard > Storage > Blob to your environment variables
- Configure upload route handler — create an API route that calls
handleUpload()from @vercel/blob for client uploads - Add content type detection — pass
contentType: file.typeor use automatic detection with the multipart upload option - Increase body size limit — export
const config = { api: { bodyParser: { sizeLimit: '10mb' } } }for server-side uploads
Real developers can help you.
Stanislav Prigodich
15+ years building iOS and web apps at startups and enterprise companies. I want to use that experience to help builders ship real products - when something breaks, I'm here to fix it.
prajwalfullstack
Hi Im a full stack developer, a vibe coded MVP to Market ready product, I'm here to help
Yovel Cohen
I got a lot of experience in building Long-horizon AI Agents in production, Backend apps that scale to millions of users and frontend knowledge as well.
Antriksh Narang
5 years+ Experienced Dev (Specially in Web Development), can help in python, javascript, react, next.js and full stack web dev technologies.
Sage Fulcher
Hey I'm Sage! Im a Boston area software engineer who grew up in South Florida. Ive worked at a ton of cool places like a telehealth kidney care startup that took part in a billion dollar merger (Cricket health/Interwell health), a boutique design agency where I got to work on a ton of exciting startups including a photography education app, a collegiate Esports league and more (Philosophie), a data analytics as a service startup in Cambridge (MA) as well as at Phillips and MIT Lincoln Lab where I designed and developed novel network security visualizations and analytics. I've been writing code and furiously devoted to using computers to make people’s lives easier for about 17 years. My degree is in making computers make pretty lights and sounds. Outside of work I love hip hop, the Celtics, professional wrestling, magic the gathering, photography, drumming, and guitars (both making and playing them)
Tejas Chokhawala
Full-stack engineer with 5 years experience building production web apps using React, Next.js and TypeScript.
Focused on performance, clean architecture and shipping fast.
Experienced with Supabase/Postgres backends, Stripe billing, and building AI-assisted developer tools.
Basel Issmail
’m a Senior Full-Stack Developer and Tech Lead with experience designing and building scalable web platforms. I work across the full development lifecycle, from translating business requirements into technical architecture to delivering reliable production systems.
My work focuses on modern web technologies, including TypeScript, Angular, Node.js, and cloud-based architectures. I enjoy solving complex technical problems and helping teams turn product ideas and prototypes into working platforms that can grow and scale.
In addition to development, I often collaborate closely with product managers, business analysts, designers, and QA teams to ensure that solutions align with both technical and business goals.
I enjoy working with startups and product teams where I can contribute both as a hands-on engineer and as a technical partner in designing and delivering impactful software.
Rudra Bhikadiya
I build and fix web apps across Next.js, Node.js, and DBs.
Comfortable jumping into messy code, broken APIs, and mysterious bugs.
If your project works in theory but not in reality, I help close that gap.
Costea Adrian
Embedded Engineer specilizing in perception systems. Latest project was a adas camera calibration system.
Jacek Rozanski
Senior PHP/Symfony developer and DevOps engineer with 20+ years of professional experience, running opcode.pl (web development agency, est. 2004).
Day job: I'm the sole backend developer at merketing company where I own and maintain 11 PHP/Symfony microservices on AWS (ECS Fargate, RDS, S3, CloudFront), handle the full CI/CD pipeline (Bitbucket Pipelines, Docker), and manage monitoring with Sentry and CloudWatch. These services handle high request volumes in production every month.
What I bring to AI-built apps:
- I audit and fix security issues (OWASP methodology), performance bottlenecks, and architectural problems in codebases generated by Cursor, Claude Code, Lovable, Bolt, and v0
- I refactor AI-generated prototypes into production-grade applications with proper error handling, testing, and clean architecture (SOLID, DDD, hexagonal architecture)
- I set up the infrastructure AI tools don't touch: AWS hosting, CI/CD pipelines, automated deployments, database optimization, monitoring, and alerting
- I integrate external services: payment providers, email systems, partner APIs, SSO/auth
Tech stack: PHP 8.x, Symfony, React, Next.js, PostgreSQL, MySQL, Docker, AWS (ECS, RDS, S3, SQS/SNS, CloudFront), Terraform, Supabase. I also use AI tools daily (Claude Code, Cursor) in my own workflow, so I understand both the strengths and the gaps in AI-generated code.
Based in Poland (CET timezone). Available for async work and calls during EU/US business hours.
You don't need to be technical. Just describe what's wrong and a verified developer will handle the rest.
Get HelpFrequently Asked Questions
What is the maximum file size for Vercel Blob?
Server-side uploads are limited to 4.5MB by the serverless function body limit. Client-side uploads support up to 500MB using the @vercel/blob/client upload() method.
How do I get the BLOB_READ_WRITE_TOKEN?
Go to Vercel Dashboard > Storage > Create Blob Store. The token is automatically added to your project environment variables.
Can I upload to Vercel Blob from the browser directly?
Yes, use the upload() function from @vercel/blob/client. You need a server-side route handler that calls handleUpload() to generate secure upload URLs.