UnAPI

According to its website, an unAPI is:

"a tiny HTTP API any web application may use to co-publish discretely identified objects in both HTML pages and disparate bare object formats. It consists of three parts: an identifier microformat, an HTML autodiscovery link, and three HTTP interface functions, two of which have a standardized response format."

The unAPI specification is only two pages long.

Server-side applications which use unAPI

 * Bebop
 * Evergreen
 * Koha
 * refbase
 * WordPress (via a plugin)
 * VITAL, digital repository
 * invenio digital library framework
 * Omeka S, web-publishing platform for academic and cultural repositories
 * Glottolog a clld app supports unAPI on its root page.

Client tools which can use unAPI

 * Zotero