npx @gltf-transform/cli inspect model.glb
npx @gltf-transform/cli optimize model.glb model.opt.glb --compress draco --texture-compress webp --texture-size 2048
npx @gltf-transform/cli inspect model.opt.glb

import * as THREE from "three";
import { GLTFLoader } from "three/addons/loaders/GLTFLoader.js";
import { DRACOLoader } from "three/addons/loaders/DRACOLoader.js";

const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setPixelRatio(window.devicePixelRatio);
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

const scene = new THREE.Scene();
const sun = new THREE.DirectionalLight(0xffffff, 2); // glTF PBR materials render black without lights or an environment
sun.position.set(3, 5, 2);
scene.add(sun, new THREE.HemisphereLight(0xffffff, 0x444444, 1.5));

const camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 0.1, 100);
camera.position.set(2, 1.5, 3);
camera.lookAt(0, 0, 0);

const gltf = await new GLTFLoader()
  .setDRACOLoader(new DRACOLoader()) // the Draco WASM decoder loads from the three package
  .loadAsync("model.opt.glb");
scene.add(gltf.scene);

function animate() {
  renderer.render(scene, camera);
}

renderer.setAnimationLoop(animate);

npx @gltf-transform/cli inspect model.glb
npx @gltf-transform/cli inspect model.opt.glb --format csv
npx @gltf-transform/cli validate model.glb --ignore ACCESSOR_WEIGHTS_NON_NORMALIZED

undefined

Main flags (booleans take an explicit value, like `--simplify false`):

- `--compress draco|meshopt|quantize` — geometry and animation compression (default `meshopt`).
- `--texture-compress ktx2|webp|avif` — texture codec (default `auto`, recompress in the original format).
- `--texture-size <px>` — cap texture dimensions, default 2048.
- `--simplify <bool>`, `--simplify-ratio <0-1>`, `--simplify-error <fraction>`, `--simplify-lock-border <bool>` — mesh simplification; ratio 0 and error 0.0001 by default.
- `--instance <bool>`, `--instance-min <count>` — GPU instancing for repeated meshes.
- `--join <bool>`, `--join-meshes <bool>`, `--join-named <bool>`, `--flatten <bool>` — draw-call reduction; `--join` requires `--flatten`.
- `--weld <bool>` — merge duplicate vertices; `draco` welds by itself even with `--weld false`, while `simplify` welds only unindexed primitives, so keep `--weld true` when simplifying.
- `--prune <bool>`, `--resample <bool>`, `--palette <bool>`, `--sparse <bool>`, `--meshopt-level medium|high`.

With `--texture-compress ktx2`, `optimize` picks bitstreams itself: UASTC for the normal, occlusion and metallic-roughness slots, ETC1S for everything else. For alternatives outside this skill's lane, gltfpack covers similar ground; gltf-transform is enough here.

npx @gltf-transform/cli draco model.glb model.opt.glb --method edgebreaker --quantize-position 14
npx @gltf-transform/cli meshopt model.glb model.opt.glb --level high
npx @gltf-transform/cli quantize model.glb model.opt.glb
npx @gltf-transform/cli gzip model.opt.glb

undefined

KTX2 output — `etc1s`, `uastc` or `optimize --texture-compress ktx2` — shells out to the `ktx` command from KTX-Software (4.4.0 or newer), so install that first; WebP and AVIF are encoded in-process. The single `etc1s` and `uastc` commands convert every texture to one bitstream; the per-slot split (UASTC for normal, occlusion and metallic-roughness, ETC1S for the rest) is what `optimize --texture-compress ktx2` does for you, and `--slots` selects texture roles by name when you need a custom split. Runtime: KTX2 needs KTX2Loader with `detectSupport`; WebP and AVIF decode in the browser.

npx @gltf-transform/cli weld model.glb model.opt.glb
npx @gltf-transform/cli simplify model.glb model.opt.glb --ratio 0.5 --error 0.001
npx @gltf-transform/cli join model.glb model.opt.glb
npx @gltf-transform/cli instance model.glb model.opt.glb --min 5
npx @gltf-transform/cli dedup model.glb model.opt.glb
npx @gltf-transform/cli prune model.glb model.opt.glb

import { GLTFLoader } from "three/addons/loaders/GLTFLoader.js";
import { DRACOLoader } from "three/addons/loaders/DRACOLoader.js";
import { KTX2Loader } from "three/addons/loaders/KTX2Loader.js";
import { MeshoptDecoder } from "three/addons/libs/meshopt_decoder.module.js";

// Wire every codec the pipeline may emit; a missing one throws at load time
const gltfLoader = new GLTFLoader()
  .setDRACOLoader(new DRACOLoader()) // KHR_draco_mesh_compression
  .setMeshoptDecoder(MeshoptDecoder) // EXT_meshopt_compression
  .setKTX2Loader(new KTX2Loader().detectSupport(renderer)); // KHR_texture_basisu

const gltf = await gltfLoader.loadAsync("model.opt.glb");
scene.add(gltf.scene);

// deps: @gltf-transform/core @gltf-transform/extensions @gltf-transform/functions draco3dgltf
import { NodeIO } from "@gltf-transform/core";
import { ALL_EXTENSIONS } from "@gltf-transform/extensions";
import { dedup, prune, weld, draco } from "@gltf-transform/functions";
import draco3d from "draco3dgltf";

const io = new NodeIO()
  .registerExtensions(ALL_EXTENSIONS) // an extension left out is dropped on read, or throws if required
  .registerDependencies({
    "draco3d.decoder": await draco3d.createDecoderModule(), // reads Draco input
    "draco3d.encoder": await draco3d.createEncoderModule(),
  });

const document = await io.read("model.glb");
await document.transform(
  dedup(),
  weld(), // shared vertices, before compression
  prune(), // drop what no Scene references
  draco({ method: "edgebreaker", quantizePosition: 14 }),
);
await io.write("model.opt.glb", document);

npx gltfjsx model.glb --transform

import * as THREE from "three/webgpu";
import { GLTFLoader } from "three/addons/loaders/GLTFLoader.js";
import { KTX2Loader } from "three/addons/loaders/KTX2Loader.js";
// renderer is an initialized WebGPURenderer (its init() was awaited)
const gltfLoader = new GLTFLoader()
  .setKTX2Loader(new KTX2Loader().detectSupport(renderer));
const gltf = await gltfLoader.loadAsync("model.opt.glb");
scene.add(gltf.scene);