This document discusses the work of the IIIF Discovery Technical Subgroup, which aims to support the discovery of IIIF resources across institutions. It notes that over 335 million IIIF resources are available from over 100 institutions. Key areas the group is addressing include: (1) how to crawl and harvest IIIF resource descriptions from different sources, (2) how to index and link IIIF content to external metadata formats to support search, and (3) how to set up change notification systems and import IIIF content into different viewers. The group is developing recommendations and reference implementations in these areas to facilitate broad discovery of the growing amount of IIIF content available online.