Bolt
api
CORS Error - Cross-Origin Request Blocked
API requests fail with CORS error: 'Access-Control-Allow-Origin header missing'. The browser blocks requests to a different domain.
Your frontend is on one domain and API on another, or localhost vs deployed URL.
Error Messages You Might See
Access to XMLHttpRequest has been blocked by CORS policy
No 'Access-Control-Allow-Origin' header
Credentials mode is 'include' but CORS allow-origin is '*'
Common Causes
- API doesn't include CORS headers in response
- API allow-origin header doesn't match request origin
- Credentials (cookies) sent without proper CORS config
- OPTIONS preflight request not handled
- Missing wildcard or specific origin in CORS config
How to Fix It
Add CORS headers to API: Response headers { 'Access-Control-Allow-Origin': '*' }
For credentials: 'Access-Control-Allow-Origin': 'https://your-domain.com' (not wildcard)
Include: 'Access-Control-Allow-Credentials': 'true'
Handle OPTIONS: if (request.method === 'OPTIONS') return new Response(null, { headers: corsHeaders })
Use middleware to apply CORS to all routes
Real developers can help you.
Prakash Prajapati
I’m a Senior Python Developer specializing in building secure, scalable, and highly available systems. I work primarily with Python, Django, FastAPI, Docker, PostgreSQL, and modern AI tooling such as PydanticAI, focusing on clean architecture, strong design principles, and reliable DevOps practices. I enjoy solving complex engineering problems and designing systems that are maintainable, resilient, and built to scale.
Omar Faruk
As a Product Engineer at Klasio, I contributed to end-to-end product development, focusing on scalability, performance, and user experience.
My work spanned building and refining core features, developing dynamic website templates, integrating secure and reliable payment gateways, and optimizing the overall system architecture.
I played a key role in creating a scalable and maintainable platform to support educators and learners globally.
I'm enthusiastic about embracing new challenges and making meaningful contributions.
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.
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.
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)
Costea Adrian
Embedded Engineer specilizing in perception systems. Latest project was a adas camera calibration system.
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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.
Taufan
I’m a product-focused engineer and tech leader who builds scalable systems and turns ideas into production-ready platforms.
Over the past years, I’ve worked across startups and fast-moving teams, leading backend architecture, improving system reliability, and shipping products used by thousands of users. My strength is not just writing code — but connecting product vision, technical execution, and business impact.
Matthew Butler
Systems Development Engineer @ Amazon Web Services
You don't need to be technical. Just describe what's wrong and a verified developer will handle the rest.
Get HelpFrequently Asked Questions
Should I use CORS wildcard '*'?
Only for public APIs. For APIs with credentials, specify exact domain
Do I need CORS for same domain?
No, CORS only applies to cross-origin (different domain/port/protocol)
What's a preflight request?
Browser sends OPTIONS request first for certain request types. Server must respond with CORS headers