64 link types across 8 categories. You probably don't need all of them. Here's how to pick.
Where to Find It
Settings → External Links (or /settings?tab=external-links).
You'll see all 64 system link types organized by category, each with a toggle. Active link types appear in the dropdown when adding external links to a book. Inactive ones don't.
The 8 Categories
Bibliographic (7 types)
WorldCat, VIAF, Wikidata, Wikipedia, ISNI, Open Library, KVK. The authority files and meta-catalogs that identify books and people across systems.
Short Title Catalogs (9 types)
ISTC, GW, USTC, ESTC, STCN, STCV, VD16, VD17, EDIT16. The specialized databases for early printed books. If you collect incunabula or books printed before 1700, these are essential. If you don't, they're noise.
National & Regional Catalogs (22 types)
Every national library catalog, from KBR to the Library of Congress, plus union catalogs like Unicat, and K10plus. Enable the ones relevant to your collection's geography.
Digital Libraries (8 types)
Gallica, Europeana, Google Books, HathiTrust, Internet Archive, MDZ, CERL HPB, Biodiversity Heritage Library. Links to digitized versions and digital catalogs.
Provenance & Specialist (4 types)
CERL Thesaurus, MEI (Material Evidence in Incunabula), data.bnf.fr, GND. For provenance research and authority data.
Antiquarian & Marketplaces (6 types)
AbeBooks, ZVAB, Biblio, viaLibri, Bookfinder, Catawiki. For tracking market presence and comparison shopping.
Auction Houses & Prices (5 types)
Rare Book Hub, Christie's, Sotheby's, Bonhams, Drouot. For auction records and price history.
Community (2 types)
Goodreads, LibraryThing. For social cataloging and reviews.
Other (2 types)
Publisher Website, Other. The catch-all categories.
Custom Link Types
Don't see the link type you need? Create your own.
In Settings → External Links, scroll to the bottom and click Add Custom Type. Give it a name, a domain (optional), and assign it to a category. Custom types appear alongside system types in the dropdown when adding links to books.
Custom types are private to your account. They won't appear for other users.
Practical Recommendations
For modern book collectors: Enable bibliographic, national catalogs for your country, digital libraries, marketplaces. Disable short title catalogs and provenance types.
For antiquarian collectors: Enable everything in short title catalogs, provenance, national catalogs. These are your daily tools. You'll also want marketplaces and auction houses.
For incunabula specialists: ISTC, GW, CERL HPB, MEI, CERL Thesaurus — these are your core references. Everything else is secondary.
For dealers: All marketplaces, all auction houses, Rare Book Hub. Plus the catalogs relevant to your stock.
The Auto-Fill Feature
When you add a book via Library Lookup, Shelvd automatically creates an external link to the source catalog. If you look up a book from the BnF, a link to the BnF record is added automatically. This only works if the relevant link type is active.
This is one reason to keep your national library link types active even if you don't add links manually — the auto-fill does it for you.
See also: External Links · Settings Guide · The 22 Providers