The European Library considers a collection to be any aggregation of physical or digital items. It is organised and catalogued in order to make its access easier for its users.

The European Library portal includes collections with digital items (note that among digital items, there are also "born digital" objects). But the portal also provides access to bibliographic and non-digital items. Any collection can be added to The European Library portal as long as the collection has associated metadata and a description which complies with The European Library Application Profile for Collections Descriptions.

The European Library portal gives access to:

-searchable collections: allow users to directly access specific objects and metadata can be harvested into The European Library Central Index via OAI-PMH or recovered via FTP or can be searched on demand in the portal via SRU or Z39.50

-browse-only collections: accessible via a link provided by The European Library, and which leads to the specific national environment. For instance, these collections cannot be harvested via OAI-PMH or FTP nor searched via SRU or Z39.50

-catalogues from national libraries chosen as the "default" theme:

-collections by theme: helps the user to launch a specific search: