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 should signal the access restrictions of the external links included in a citation. Nota bene: access icons do not display correctly for editors who use Modern skin.

Four access levels can be used:
 * access indicator for named identifiers:
 * Lock-green.svg : the source is free to read for anyone
 * access indicators for url-holding parameters:
 * Lock-gray-alt-2.svg : a free registration is required to access the source
 * Lock-gray-alt-2.svg : there are other constraints (such as a cap on daily views) to freely access this source
 * Lock-red-alt-2.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 indicators for url-holding parameters
Sources linked by url, chapter-url, entry-url, article-url, and section-url are presumed to be free-to-read. When they are not free-to-read, editors should mark those sources with the matching access-indicator parameter so that an appropriate icon is included in the rendered citation. Because the sources linked by these url-holding parameters are presumed to be free-to-read, they may not be marked as.

†contribution-url-access not currently defined; use its alias chapter-url-access

Access indicator for named identifiers
Links inserted by named identifiers are presumed to lie behind a paywall or registration barrier – exceptions listed below. When they are free-to-read, editors should mark those sources with the matching access-indicator parameter so that an appropriate icon is included in the rendered citation. Because the sources linked by these named-identifier parameters are not presumed to be free-to-read, they may not be marked as,  , or.

Some named-identifiers are always free-to-read. For those named-identifiers there are no access-indicator parameters, the access level is automatically indicated by the template. These named identifiers are:
 * arxiv
 * biorxiv
 * citeseerx
 * pmc
 * rfc
 * 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: (deprecated) For online sources that require registration, set yes (or, or  ); yields to subscription if both are set. Use the appropriate access-indicator parameter
 * subscription: (deprecated) For online sources that require a subscription, set yes (or, or  ); supersedes registration if both are set. Use the appropriate access-indicator parameter