IIIF Image API Thumbnails Break with !w,h (sizeByConfinedWh): Level 1 Servers Are Not Guaranteed to Support It
A IIIF viewer generated thumbnails with full/!w,h/ (sizeByConfinedWh), and thumbnails stopped rendering for some collections backed by an external IIIF Image API. The cause: !w,h is not a required feature at Image API level 1. This walks through the level/supports relationship, the measured behavior, and switching to width-only sizing (sizeByW).
iiifthumbnaildigital-archivesimage-api