Mapbox GL JS v2.3 introduces new 3D features, performance enhancements, and expanded data-driven styling options, including a fog effect that adds depth to maps and allows designers to simplify styles. Fog can be easily implemented using the map.setFog(..) function, offering controls for color, range, and horizon-blend. The update also includes a new API for client-side elevation querying, which uses Digital Elevation Model tiles to generate terrain elevation profiles quickly and without server requests. Performance improvements involve a reduced GPU memory footprint for terrain, optimized tile cover to minimize DEM tile requests, and per-frame batching of DOM operations to enhance update performance. Additionally, data-driven styling has been expanded to line-dasharray and line-cap properties, allowing for more efficient layer management. The update is available via CDN and NPM, and further details can be found in the v2.3.0 release notes.