# Debugging CORS Without Guessing


A practical way to reason about CORS errors, preflight requests, credentials, and browser behavior.

This guide is the canonical guide page for related tools on ilham.dev. It should grow into practical explanations, caveats, examples, and references instead of creating one thin article per utility.

## Related tools

- [CORS Checker](/tools/cors-checker/) — Check whether a URL can be read from this browser origin and inspect visible CORS headers.

## Notes for future edits

- Keep the guide reusable and factual.
- Link to personal posts only when there is a real incident, measurement, migration, or lesson.
- For sensitive inputs, mention whether the related tool runs locally in the browser and warn against pasting production secrets without understanding the trust boundary.