You've probably seen this error before...
...so your first instinct is to ask a LLM how to solve it, which gets you nowhere
The truth is CORS sucks. Most developers struggle to understand it so they...
Sounds familiar? You're not alone.
Here's the thing about CORS that nobody talks about:
CORS is genuinely complex. The browser security model evolved over decades as an patchwork of fixes and additions. Same-Origin Policy came first, then CORS was bolted on top to create exceptions.
The result? Multiple moving parts, vague error messages, and behavior that changes between browsers.
You're not struggling with CORS because you're a bad developer. You're struggling because the web security model is inherently complicated and most tutorials only show you the 'happy path' without explaining what happens when things go wrong. They don't show you how to think through CORS problems systematically, or how to debug them when they inevitably break.
That's exactly why we built this course: a clear, hands-on explanation of how CORS actually works, with real scenarios you can practice on.
Here's how we'll turn your CORS
frustration into a skill
The course is structured in eight lessons that take you from zero. Each lesson builds on the previous one, creating a clear path.
Every concept is explained in depth with real examples. No surface-level overviews or hand-wavy explanations. We walk you through exactly how and why things work the way they do.
Interactive widgets let you experiment as you learn. Change headers, modify requests, and see exactly how the browser responds in real-time without leaving the lesson.
12 hands-on labs help you put theory into practice. You'll work in a real code editor with step-by-step guidance.
Introduction to browser security
Why browsers became security-focused and what threats they're designed to prevent.
The browser's sandbox
How the browser's security model isolates different websites from each other.
Introduction to browser site isolation
How modern browsers separate sites at the process level and what this means for your applications.
Same-Origin Policy
The foundation of web security. You'll understand exactly what cross-origin interactions the browser allows or blocks, and why. Four hands-on labs let you experiment with different scenarios and see the policy in action.
Cross-Origin Resource Sharing (CORS)
The main event. How CORS creates exceptions to Same-Origin Policy, what each header does, when preflight requests trigger, and how to debug issues systematically.
Bypassing CORS locally
Practical techniques for development: browser flags, proxy setups, and local development strategies that won't come back to bite you in production.
Fixing CORS issues in cloud platforms
Real-world deployment scenarios across AWS, Vercel, Netlify, and other platforms.
CORS security disasters to avoid
Learn from others' mistakes. Practical guide on how to implement CORS securely.
Our promise: after this course, you'll...
Built for how developers actually learn best
Every concept is explained with real examples, then reinforced with hands-on practice. Learn, practice, master. That's our secret sauce.
Interactive
Change headers, modify requests, and watch the browser respond in real-time.
Step-by-step guidance
Never get stuck wondering what to do next.
Built-in code editor
Work in an actual code editor with syntax highlighting and instant feedback.
Zero Setup
Everything runs in your browser. No downloads, no configurations.
Ready to never Google 'CORS Error' again?
This is the CORS course we wish existed when we were learning web development. One purchase, lifetime access, future updates included.
Early Access
40% limited time pre-sale offer
Price increases to $99 after launch. Includes lifetime access and all updates.
- Lifetime access to all labs and lessons
- Certificate of completion
- All future updates included
- Money-back guarantee
Course launches Q4 2025. You'll be notified immediately when it's ready. Secure payment through Stripe. Questions? Email hello@i-hate-cors.com
Frequently Asked Questions
Everything you need to know about the course, access, and what to expect.
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