Introducing glTF 2.1 with Complex Scenes
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Introducing glTF 2.1 with Complex Scenes
June 11, 2026<br>by The Khronos 3D Formats Working Group
gltf
Since the release of glTF™ 2.0 in 2017, the format has matured into a rich ecosystem spanning mesh compression, texture optimization, 3D Gaussian splats, and more. Today, the Khronos® 3D Formats Working Group is excited to announce plans for glTF 2.1: a focused, backward-compatible revision of the core specification, built around a single motivation — making glTF work as well for large, composed scenes as it already does for single assets .
Every feature in this release addresses a real gap that today forces teams toward proprietary conventions, custom tooling, or workarounds that break interoperability:
Asset creators and pipeline teams can include preview thumbnails directly in glTF files, making asset libraries browsable without a renderer
Developers building large-scale scenes now have a standardized way to compose and deliver multi-file scene graphs for digital twins, building information modeling (BIM), smart cities, geospatial, and simulation
Engine and runtime developers get standardized spatial primitives through Shapes and Bounding Volume Hierarchies, expanded accessor component type definitions for extensions to build on, and Unique IDs that make object addressing stable and interoperable across tools
Developers who need 3D streaming can build on complex scenes as the foundation for progressive delivery, including the spatial subdivision, availability maps, LOD and quality metrics, and streaming hints already proven at scale by the glTF extensions of OGC 3D Tiles
Everyone benefits from a 64-bit GLB format that lifts the 4 GiB size ceiling, and a cleaner specification with the rarely-used multiple-scenes pattern formally deprecated
Every capability in glTF 2.1 holds to glTF's core mission as a delivery format: the efficient, reliable transmission and loading of 3D assets at runtime. Complex scenes extend what glTF can deliver — complete, composed, multi-asset experiences rather than single models — without turning glTF into an authoring or interchange format. glTF 2.1 is complementary to content creation ecosystems such as OpenUSD: scenes authored and assembled in creation pipelines can now be delivered, self-contained and interoperable, as glTF.
"This release has been guided by a clear philosophy: address the most impactful, widely needed improvements to the core spec while keeping glTF lean, interoperable, and backward-compatible," said Amanda Morgan, Khronos 3D Formats co-chair and senior director, Open Standards at Bentley Systems. "Each feature has gone through a structured 'Design First' process: working groups agreed on purpose, scope, behavior, and relationships before any schema work began, ensuring that every addition earns its place in the core."
Here's what's coming.
Complex Scenes
A factory digital twin is built from thousands of equipment models. A city block is composed of buildings, infrastructure, and terrain. A simulation environment is stitched together from assets supplied by many vendors. Scenes like these are assembled, not authored as single files — yet glTF 2.0 offers only two ways to deliver them: collapse everything into one monolithic file, or adopt proprietary conventions for multi-file composition. Neither preserves the interoperability that makes glTF valuable, and this gap has been one of the primary barriers to adopting glTF at this scale.
glTF 2.1 closes the gap with a coordinated set of core features. For scene composition, External Assets lets a glTF file reference other glTF files and instantiate them in its scene hierarchy at load time, while Packaging delivers a composed scene and all of its dependencies as a single self-contained asset. For spatial primitives, implicit volumes enter the core specification through Shapes, and Bounding Volume Hierarchies use them to make large scenes efficient to cull, stream, and query. Beneath both sits Unified File References — a single, consistent mechanism for resolving external, embedded, and packaged resources that the rest of the architecture depends on.
Together, these capabilities allow a complete, structured, multi-file scene to be delivered as one interoperable glTF asset — and they form the foundation on which features like progressive scene streaming, LOD hierarchies, distributed asset libraries, and large-scale collaborative environments can be built. They also render one piece of the 2.0 specification obsolete: glTF 2.1 formally deprecates the rarely-used multiple-scenes pattern, described at the end of this section.
External Assets
With External Assets, a glTF file can declaratively reference other glTF files...