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 restrictions on access to material provided via the external links included in a citation. These levels describe requirements or constraints related to accessing and viewing the cited material; they are not intended to indicate the ability to reuse, or the copyright status, of the material, since that status is not relevant to verifying claims in articles.

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, each value is attributed to a specific external link.

Access indicators for url-holding parameters
Online sources linked by url, article-url, chapter-url, contribution-url, entry-url, map-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.

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