How to use CORS Tester
- Start by adding the text you want to check into CORS Tester.
- Use the Paste the response headers, Request origin, Request method settings to control the result.
- The result is computed live in your browser as you edit the input.
- Use Copy to keep or reuse the result.
About this tool
Everything CORS Tester does happens on your own device. CORS Tester is a free HTTP & Security Header Tools utility that runs in your browser, doing its work on the input you provide without a backend.
Because it runs on your device, it is fast and private and works offline once loaded. No data is sent anywhere, so it stays fast and private by default.
Frequently asked questions
What is CORS Tester for?
Use CORS Tester to check your input without installing anything using the Paste the response headers, Request origin controls; everything happens client-side.
Does CORS Tester cost anything?
No — CORS Tester is completely free, with no sign-up and no hidden limits.
Where is my data processed by CORS Tester?
Entirely in your browser — CORS Tester keeps your data on your own machine and sends nothing anywhere.
Can I use CORS Tester without a connection?
Yes — after the first load CORS Tester runs entirely offline.