Template:Citation Style documentation/registration

 Citations of online sources that require registration or a subscription are acceptable in Wikipedia as documented in Verifiability – Access to sources. As a courtesy to readers and other editors, editors can signal the access restrictions of the external links included in a citation.

Four access levels can be used:
 * Lock-green.svg : the source is free to read for anyone (this applies in particular to articles in open access)
 * Lock-blue-alt-2.svg : a free registration is required to access the source
 * Lock-blue-alt-2.svg : there are other constraints (such as a cap on daily views) to freely access this source
 * Lock-red-alt.svg : the source is only accessible via a paid subscription ("paywall")

As there are often multiple external links with different access levels in the same citation, these values are attributed to a particular external link.

Access level of url
Links inserted with url are expected to be free to read by default. If not, editors can use one of to indicate the relevant access restriction.
 * subscription
 * registration
 * limited

Access level of identifiers
Links inserted by identifiers such as doi are not expected to offer a free full text by default. If they do, editors can use free (in the case of doi) to indicate the relevant access level. The following identifiers are supported:
 * bibcode with free
 * doi with free
 * hdl with free
 * jstor with free
 * ol with free
 * osti with free

Some identifiers always link to free full texts. In this case, the access level is automatically indicated by the template. This is the case for arxiv, biorxiv, citeseerx, pmc, rfc and ssrn.

Ambiguous access parameters
The parameters yes and yes can also be used to indicate the access level of a citation. However, they do not indicate which link they apply to, so editors are encouraged to use registration and subscription instead, when the restriction applies to url. If the restriction applies to an identifier, these parameters should be omitted.

These parameters add a link note to the end of the citation: Setting registration or subscription to any value other than,  , or   will generate an error message.
 * registration: For online sources that require registration, set yes (or, or  ); superseded by subscription if both are set.
 * subscription: For online sources that require a subscription, set yes (or, or  ); supersedes registration if both are set.