Editing Module:Cite IUCN/doc (section)

===Old-style and new-style IUCN urls===

Until late 2018, the IUCN assessments used urls of form 

:<code><nowiki> http://www.iucnredlist.org/details/15955/0</nowiki></code>
:where 15955 is the taxon ID and the “0” suffix indicates a global assessment (other single digit numbers code for various regional assessments).

From around September 2018, the IUCN switched to a new format for the url, of the form

:<code><nowiki> https://www.iucnredlist.org/species/15955/50659951</nowiki></code>
:where the 15955 is the taxon ID and a unique suffix identies a version of an assessment. This left all Wikipedia links to IUCN assesssments as dead links. 

Shortly afterwards the IUCN produced a backup of the old system with links of the form

:<code><nowiki> http://oldredlist.iucnredlist.org/details/15955/0</nowiki></code>
: which uses an old-style url form on the oldredlist subdomain. Many citations were switched over to this url. However, this  subdomain was shut down near the end of 2019, leaving many dead links generating [http://oldredlist.iucnredlist.org/details/15955/0 502 Bad Gateway] errors.