CORS Headers Missing After API Refactoring
After Cursor refactored your API server, requests from the frontend are blocked by CORS errors. The browser blocks responses due to missing Access-Control headers.
CORS middleware was removed or misconfigured.
Error Messages You Might See
Common Causes
- CORS middleware removed or commented out
- Origin whitelist too restrictive or changed
- Allow-Methods not including required methods (PUT, DELETE)
- Allow-Headers not including custom headers (Authorization)
- Credentials handling broken (withCredentials vs CORS)
How to Fix It
Enable CORS: app.use(cors({origin: 'http://localhost:3000', credentials: true})). Or manually set headers: res.setHeader('Access-Control-Allow-Origin', '*'). Ensure preflight handled: OPTIONS method. Allow methods: GET, POST, PUT, DELETE.
Real developers can help you.
Anthony Akpan
Developer with 8 years of experience building softwares fro startups
ISHANTDEEP SINGH
Senior Software Engineer with 7+ years of experience in React, JavaScript, TypeScript, Next.js, and Node.js. I’ve also worked as a tech lead for startups, owning end-to-end technical execution including architecture, development, scaling, and delivery. I bring a strong mix of hands-on coding, product thinking, and technical leadership, and I’m comfortable building products from scratch as well as improving and scaling existing systems.
Kingsley Omage
Fullstack software engineer passionate about AI Agents, blockchain, LLMs.
Victor Denisov
Developer
Costea Adrian
Embedded Engineer specilizing in perception systems. Latest project was a adas camera calibration system.
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)
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.
Jaime Orts-Caroff
I'm a Senior Android developer, open to work in various fields
AUXLE
I am a Full Stack Developer experienced in building Websites, Web apps and Cross Platform Mobile Apps for Startups and Companies.
Bastien Labelle
Full stack dev w/ 20+ years of experience
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's a preflight request?
Browser sends OPTIONS request first to check permissions for complex requests (PUT, DELETE, custom headers). Server must respond with CORS headers.
When is CORS needed?
When frontend (different origin) calls API. Not needed for same-origin. Localhost:3000 != localhost:3001.