# CORS Checker Guide

Check whether a URL can be read from this browser origin and inspect visible CORS headers.

- Tool: https://ilham.dev/tools/cors-checker/
- Guide URL: https://ilham.dev/guides/cors-checker/
- Tool guides index: https://ilham.dev/guides/tools/
- Broader guide: Debugging CORS Without Guessing (https://ilham.dev/guides/debugging-cors/)

## What it does

Check whether a URL can be read by JavaScript from this site origin. The tool sends a browser fetch request and, where possible, an OPTIONS-style probe, then reports what the browser allowed the page to see. It cannot spoof arbitrary Origin headers because browsers deliberately do not allow that.

## Use the tool

Open https://ilham.dev/tools/cors-checker/, add the input the tool asks for, run it, and check the output before using it elsewhere.

## Input and output

- Input: text.
- Output: text.
- Category: Network.

## Privacy and processing
This tool needs a network request to complete the lookup or test. Send only data you are comfortable sharing with the target service.

## Questions

### Why does it say blocked without showing the server headers?

When CORS blocks a response, the browser hides the response from JavaScript. That is the rule this tool is testing, so sometimes the only honest answer is that the page could not read the details.