The International Image Interoperability Framework (IIIF, spoken as 'triple-I-eff') defines several application programming interfaces that provide a standardised method of describing and delivering images over the web, as well as "presentation based metadata" (that is, structural metadata) about structured sequences of images. If institutions holding artworks, books, newspapers, manuscripts, maps, scrolls, single sheet collections, and archival materials provide IIIF endpoints for their content, any IIIF-compliant viewer or application can consume and display both the images and their structural and presentation metadata.

There are many digitisation programmes that have resulted in a particular collection’s content exposed on the web in a particular viewer application, but these various collections have not typically been interoperable with one another, and end users or institutions cannot substitute a viewer of their choice to consume the digitised material. The IIIF aims to cultivate shared technologies for both client and server to enable interoperability across repositories, and to foster a market in compatible servers and viewing applications.