Response ModifyCORS & Cache• 4 min read

How to Bypass CORS Errors and Modify Response Headers

Summary: Inject `Access-Control-Allow-Origin: *` and customize caching directives to test cross-origin APIs and inspect stale-while-revalidate behavior.

Why This Rule Matters for Developers & QA

CORS preflight failures are among the most common blockers when integrating third-party APIs or running localhost frontends against remote staging APIs. Response Header modification eliminates CORS errors instantly.

Step-by-Step Implementation Guide

1

Select Cross-Origin Target URL

Enter the domain of the remote API causing CORS issues (e.g. `https://api.externalpartner.com/*`).

2

Inject CORS Headers

Add `Access-Control-Allow-Origin: *` and `Access-Control-Allow-Headers: *`.

3

Refresh the Application

The browser receives the required permissive headers and executes the fetch request without blocking.

Configuration Snippet

How to Bypass CORS Errors and Modify Response Headers — proxyceptor-rule.json
JSON
{
  "id": "rule_bypass_cors",
  "pattern": "https://api.externalpartner.com/*",
  "action": "modify-response-headers",
  "responseHeaders": {
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, OPTIONS",
    "Access-Control-Allow-Headers": "Content-Type, Authorization",
    "Cache-Control": "no-store, no-cache, must-revalidate"
  },
  "enabled": true
}

Frequently Asked Questions

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