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:
free: the source is free to read for anyone
- access indicators for url-holding parameters:
registration: a free registration is required to access the source-
limited: there are other constraints (such as a cap on daily views) to freely access this source 
subscription: 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=, |article-url=, |chapter-url=, |contribution-url=, |entry-url=, |map-url=, and |section-url= are presumed to be free-to-read.[1] 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 free.
| url | access | allowed keywords |
|---|---|---|
|url= |
|url-access= |
registration limited subscription
|
|article-url= |
|article-url-access=
| |
|chapter-url= |
|chapter-url-access=
| |
|contribution-url= |
|contribution-url-access=
| |
|entry-url= |
|entry-url-access=
| |
|map-url= |
|map-url-access=
| |
|section-url= |
|section-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 limited, registration, or subscription.
| identifier | access | allowed keywords |
|---|---|---|
|bibcode= |
|bibcode-access= |
free
|
|doi= |
|doi-access=
| |
|hdl= |
|hdl-access=
| |
|jstor= |
|jstor-access=
| |
|ol= |
|ol-access=
| |
|osti= |
|osti-access=
| |
|s2cid= |
|s2cid-access=
|
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=