How-to guides on header — website metadata toolkit

Inspect social preview metadata

Mon, 01 Jan 0001 00:00:00 +0000

Fetch a page and focus on the metadata that social platforms use:

header extract --style opengraph https://example.com
header extract --style twitter https://example.com

The output only includes properties found on the page; an absent Open Graph image, for example, is not invented.

To run built-in metadata checks:

header lint https://example.com
header lint --list all https://example.com

To generate a PNG preview card from a webpage:

header card list
header card file --out card.png https://example.com

The card file is written locally. Be aware that downloaded website images remain the property of their respective owners.

Trace redirects

Mon, 01 Jan 0001 00:00:00 +0000

Trace redirects

To follow HTTP redirects and HTML meta-refresh redirects:

header trace-redirects https://example.com

Use header trace-redirects --help for the current redirect limit, delay and cookie options. Avoid using the fetcher as an unrestricted proxy in a privileged network environment; see the repository’s security policy.

Troubleshooting

Mon, 01 Jan 0001 00:00:00 +0000

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: