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OpenURL & COinS

COinS embeds an OpenURL ContextObject inside an HTML page using . Wikipedia uses it on every citation.

COinS — Context Objects in Spans — is a microformat for embedding OpenURL ContextObjects inside HTML pages. A browser extension or client-side script reads the page, finds COinS spans, and offers the reader a resolution link through their institutional resolver. COinS uses the Inline transport of Z39.88-2004 (see Transports).

Syntax

A COinS span is an empty <span> element with class Z3988 whose title attribute carries a KEV-form ContextObject:

<span class="Z3988"
      title="ctx_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.atitle=Can+Quantum-Mechanical+Description+of+Physical+Reality+Be+Considered+Complete%3F&rft.jtitle=Physical+Review&rft.aulast=Einstein&rft.date=1935&rft.volume=47&rft.spage=777">
</span>

The body of the span is empty by convention. The title attribute holds the KEV ContextObject exactly as it would appear in a query string, less the leading ? and the base URL. Ampersands inside the attribute are escaped as &amp; per HTML rules.

How it is used

A client-side tool — a browser extension such as one provided by a library, or a JavaScript include on a discovery page — scans the page for elements with class Z3988. For each, it extracts the title, prepends the user's resolver base URL, and inserts a clickable link near the span. The user clicks, the resolver does its work, and the user is directed to an appropriate copy.

Where COinS appears

  • Wikipedia. Every Wikipedia citation, generated from a template such as {{cite journal}} or {{cite book}}, emits a COinS span. Library extensions can therefore add OpenURL links to every reference on an article page.
  • Reference managers. Zotero, in particular, uses COinS as one of several signals for capturing citations from a web page.
  • Institutional repositories and some publisher reference lists embed COinS for the same purpose.

Notes

  • COinS is not part of Z39.88-2004 proper; it is a community-developed convention that makes use of the Inline transport defined by the standard.
  • The class name Z3988 (no hyphen, no period) is the agreed marker.
  • COinS uses only the KEV serialization. XML COinS spans are not part of the convention.
  • The microformat predates many modern semantic-HTML practices; newer linked-data conventions (microdata, JSON-LD, schema.org) have not displaced it in scholarly contexts.

Sources