Troubleshooting
| Symptom | First check |
|---|---|
| The request fails | Confirm the URL is reachable and that the host accepts your client and User-Agent |
| A metadata field is missing | Inspect the source document; header does not fabricate absent properties |
| A rendered output is unexpected | Run header extract --style json URL and compare the raw parsed properties |
| A generated card fails | Verify destination permissions and image availability |
To diagnose a page with the built-in rules:
header extract --test https://example.com
header verify https://example.comBefore publishing diagnostics, remove private URLs, credentials, cookies and personal data. Reproduce the problem with a small public test page if possible. To report a reproducible bug, use GitHub Issues.