I3S is an open format for streaming massive 3D geospatial content. Adopted by Open Geospatial Consortium (OGC), the latest update, I3S OGC 1.3 dramatically improves performance and scalability and supports a new Building Scene Layer type. We’ll review these improvements, including paged node access pattern, a more compact geometry layout, advanced material definitions property, and support for KTX2 compressed textures – reducing compressed texture content size by over 60%. We’ll also outline patterns for distributing I3S content through open-source solutions such as loaders.gl and CesiumJS.