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.
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=