Inspect social preview metadata
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.comThe 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.comTo generate a PNG preview card from a webpage:
header card list
header card file --out card.png https://example.comThe card file is written locally. Be aware that downloaded website images remain the property of their respective owners.
GitHub repository card quality
For a https://github.com/OWNER/REPO page, the card generators use the repository identity from the URL as the title and strip GitHub’s known account-creation suffix from Open Graph/Twitter descriptions. They do not change the original fetched PageInfo; header extract --style json continues to report the page’s actual metadata.
The description is still derived from the original page and may not match its author’s preferred public description. When no meaningful description remains, header card file, card clipboard, and card stdout emit card-quality: needs-owner-description to standard error. A valid PNG is a candidate, not publication approval. Review source and selected copy before sharing.
This deliberately avoids making hundreds of separate GitHub REST API calls during batch generation. If a separate catalogue already holds GitHub repository descriptions, preserve that data and its provenance for the owner’s review.