Blocked by CORS policy, getting 401 or 403 on valid requests, or an API that works in Postman but fails in the browser? We trace the request, fix the server CORS config, preflight handling and token auth, then test it from your actual frontend so every call succeeds.
Is this your problem?
The browser console says your request was blocked by CORS policy.
You get 401 Unauthorized or 403 Forbidden on requests that should work.
The API works in Postman or curl but fails from your frontend.
Login works locally but breaks after deployment.
Why this happens
CORS and auth errors usually come from a few causes: the server does not send the right CORS headers for your frontend's origin, preflight OPTIONS requests are not handled, cookies or credentials are not allowed across domains, or tokens are sent in the wrong format, have expired or are not refreshed. Postman does not enforce CORS, which is why requests work there and fail in the browser.
What we do
Trace the failing request from browser to server.
Fix the server config — allowed origins, methods, headers and preflight.
Fix authentication — token format, expiry, refresh and cookie settings.
Test from your actual frontend in each environment you use.
What you get
Working API calls from your browser and app
Config changes committed to your repository
A plain-English explanation of what was wrong
What we need from you
A screenshot of the error (browser console or network tab)
Access to the API and frontend repositories
Common cases we handle
Express, NestJS, Django, FastAPI, Flask, Laravel and Spring Boot APIs
React, Next.js, Vue and mobile frontends
JWT, OAuth, session cookies, Firebase, Supabase and Clerk auth
APIs behind Nginx, Vercel, AWS API Gateway or Cloudflare
Pricing and turnaround
Starting price | From $20 |
Delivery | Typically 24h |
Priority delivery | 12h for +50% |
Guarantee | Works-or-refund (Quick Fix) |
Every task gets a fixed price, confirmed after the free scope check. Your code and data are used only for this task, and we sign an NDA on request.
How it works
Submit your task. Tell us what you need and share the files or access listed above.
Free 30-minute scope check. An engineer confirms the scope and gives you a fixed price before any work starts.
We do the work. Your task is handled by Codersarts' own engineering team — not a freelancer marketplace.
Delivery and handover. You get the deliverables, a walkthrough of what changed, and time to ask questions.
Related tasks
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AI-Generated Code Review — to check AI-generated code for more hidden issues.
Integrate OpenAI or Claude API — to add an AI feature to your app.
Need more than a single task?
If your app has deeper backend problems, see Codersarts Build Solutions.
FAQ
How much does it cost to fix a CORS error?
From $20 for a Quick Fix. The fixed price is confirmed after a free 30-minute scope check.
How fast will it be fixed?
Typically within 24 hours. Priority 12-hour delivery is available for +50%.
What if it is not fixed?
Quick Fix tasks are works-or-refund.
Why does my API work in Postman but not the browser?
Browsers enforce CORS and Postman does not. The fix is on the server — it must allow your frontend's origin and handle preflight requests.
Is my code confidential?
Yes. Access is used only for this task, and we sign an NDA on request.
Prefer to learn it yourself? Explore hands-on courses at Codersarts Labs.