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Browser CORS Error

Warninggeneral

Overview

Browser CORS (Cross-Origin Resource Sharing) error means a web page tried to access a resource from a different domain that has not allowed it.

Key Details

  • Access to fetch at URL has been blocked by CORS policy
  • Security feature preventing unauthorized cross-origin requests
  • Only affects browser requests, not server-to-server
  • Server must include Access-Control-Allow-Origin header

Common Causes

  • API server missing CORS headers
  • Wrong origin in Access-Control-Allow-Origin
  • Preflight OPTIONS request failing
  • Credentials included without proper CORS configuration

Steps

  1. 1For developers: add Access-Control-Allow-Origin header on the API server
  2. 2Use a CORS proxy for development testing
  3. 3Check browser console for the specific CORS error
  4. 4Verify OPTIONS preflight request is handled correctly

Tags

browsergeneralcors errorfixtroubleshooting

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Frequently Asked Questions

Cross-Origin Resource Sharing — a security mechanism that controls which domains can access an API.