Common Issues general

API Calls Failing With Errors in My AI App

Your app makes calls to an API (its own backend, Supabase, or a third-party service) and those calls fail. You see errors in the console like 500, 403, 404, or CORS errors.

Error Messages You Might See

CORS policy: No 'Access-Control-Allow-Origin' header 500 Internal Server Error 403 Forbidden 401 Unauthorized net::ERR_CONNECTION_REFUSED Timeout: request took too long
CORS policy: No 'Access-Control-Allow-Origin' header500 Internal Server Error403 Forbidden401 Unauthorizednet::ERR_CONNECTION_REFUSEDTimeout: request took too long

Common Causes

  • CORS not configured — browser blocks requests from your domain to the API
  • API key or auth token expired, missing, or wrong
  • API endpoint URL is wrong (still pointing to localhost or old URL)
  • Rate limiting — too many requests in a short time
  • Backend server error (500) due to unhandled exceptions

How to Fix It

  1. Open browser Network tab (F12 > Network) and find the failing request — check the status code and response body
  2. For CORS errors: configure your API server to allow requests from your frontend domain
  3. For 401/403: check that your API key or auth token is being sent correctly in the request headers
  4. For 500: check server logs for the actual error — the frontend error won't have details
  5. For timeouts: check if the API endpoint is accessible from your deployment environment

Real developers can help you.

Krishna Sai Kuncha Krishna Sai Kuncha Experienced Professional Full stack Developer with 8+ years of experience across react, python, js, ts, golang and react-native. Developed inhouse websearch tooling for AI before websearch was solved : ) Yovel Cohen 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. Tejas Chokhawala 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. Kingsley Omage Kingsley Omage Fullstack software engineer passionate about AI Agents, blockchain, LLMs. Richard McSorley Richard McSorley Full-Stack Software Engineer with 8+ years building high-performance applications for enterprise clients. Shipped production systems at Walmart (4,000+ stores), Cigna (20M+ users), and Arkansas Blue Cross. 5 patents in retail/supply chain tech. Currently focused on AI integrations, automation tools, and TypeScript-first architectures. Nam Tran Nam Tran 10 years as fullstack developer Stanislav Prigodich 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. Rudra Bhikadiya 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. Taufan 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. Milan Surelia Milan Surelia Milan Surelia is a Mobile App Developer with 5+ years of experience crafting scalable, cross-platform apps at 7Span and Meticha. At 7Span, he engineers feature-rich Flutter apps with smooth performance and modern UI. As the Co-Founder of Meticha, he builds open-source tools and developer-focused products that solve real-world problems. Expertise: 💡 Developing cross-platform apps using Flutter, Dart, and Jetpack Compose for Android, iOS, and Web. 🖋️ Sharing insights through technical writing, blogging, and open-source contributions. 🤝 Collaborating closely with designers, PMs, and developers to build seamless mobile experiences. Notable Achievements: 🎯 Revamped the Vepaar app into Vepaar Store & CRM with a 2x performance boost and smoother UX. 🚀 Launched Compose101 — a Jetpack Compose starter kit to speed up Android development. 🌟 Open source contributions on Github & StackOverflow for Flutter & Dart 🎖️ Worked on improving app performance and user experience with smart solutions. Milan is always happy to connect, work on new ideas, and explore the latest in technology.

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Frequently Asked Questions

What does a CORS error mean?

CORS (Cross-Origin Resource Sharing) is a browser security feature. It means your frontend (e.g., on Vercel) is trying to call an API on a different domain, and that API hasn't been configured to allow it.

I get a 500 error but don't know what's wrong. How do I find out?

A 500 error means the server crashed. The actual error is in the server logs, not in the browser. Check your hosting platform's logs.

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