Following our announcement of Unity 6.3 LTS, we are diving deep into the technical details. This version represents the first Long-Term Support release since 6.0, bringing significant stability improvements, the new Box2D v3 integration, Enhanced Audio Foundation, and a massive list of production-ready fixes.

Below is the complete breakdown of Known Issues, API Changes, and the full changelog for version 6000.3.0f1.

⚠️ Critical Known Issues

Before upgrading, please be aware of the following known issues in 6000.3.0f1:

• Core Runtime: Editor hangs when ComponentSystemGroup updates in itself (UUM-128197).

• IL2CPP: [iOS] [Android] External library generics fail during IL2CPP build (UUM-125284).

• Mesh: Crash on SkinnedMeshRendererManager when interacting with a prefab generated with uncombined meshes using Synty Sidekick Character Creator (UUM-128966).

• Metal: Game freezes after command buffer Timeout error (UUM-125778).

• Metal: [iOS] Screen flashing after the iOS splash screen (UUM-121453).

• Serialization: Exceedingly long wait on InspectorWindow.Repaint when selecting a large SVG file in the Project window (UUM-120424).

New Entries (Since 6000.3.0b10)

If you were using the beta, here are the changes specifically added between beta 10 and the final LTS release.

API Changes

• Package: Deprecated: Multiplayer Widgets are deprecated in favor of Unity Building Blocks.

Fixes (Since Beta 10)

• 2D: Fixed an issue where 2D shadows could disappear after a domain reload.

• Adaptive Performance: Improved domain reload time; packages now only updated when opening Settings.

• Android: Fixed visible icon artifact on Android XR splash screen; fixed gamepad buttons getting stuck; fixed build failures with RenderDoc.

• Animation: Fixed crash when deleting playable output with null graph; fixed Animator state normalized time stopping.

• Audio: Fixed performance regression with audio source; fixed Inspector link for AudioSnapshot.

• DX12: Fixed crash when capturing a frame in RenderDoc with “tight alignment” enabled; fixed corruption in constant buffers on async compute queue.

• Editor: Multiple fixes including layout restoration, AudioRandomContainer UI flickering, crash with shadow pass textures, and Raycast failures with default constructors.

• GI: Fixed issue upgrading projects with Light Transport package; fixed APV scenario blending on MacOS.

• Physics: Fixed crash calling Rigidbody.Move on disabled components; fixed Cloth component crash with TextMesh.

• UI Toolkit: Fixed color space bugs in filters; fixed SVG import crashes; fixed blend modes for Additive and Multiply.

• Video: Security Fix: Addresses high-severity vulnerabilities (CVE-2023-6349, CVE-2024-5197, CVE-2025-5283) via targeted code changes.

Full Features & Highlights

The major new additions in Unity 6.3 LTS.

Physics & 2D

• New Box2D v3 API: Added new low-level 2D physics API based upon Box2D v3. This currently runs alongside the existing API but will eventually replace it.

• 2D Rendering: Added Mesh Renderer and Skinned Mesh Renderer 2D workflow support for 2D URP.

• Ortho Culling: LowLevelPhysics2D renderer now performs orthographic render culling, improving debug rendering performance.

Graphics & Rendering

• Unified Raytracing API: Published API for creating cross-platform ray tracing shaders.

• xAtlas Lightmap Packing: Added a new lightmap packing algorithm based on xAtlas (now the default for new scenes).

• URP Enhancements: Added Kawase and Dual filtering options for Bloom (optimized for mobile). Added “On Tile Post Processing” for untethered XR platforms.

• Shader Graph: Added template browser; support for additional UV channels; new options for Unlit targets (Keep Lighting Variants, Decal Blending).

Editor & Workflow

• Main Toolbar: The Editor’s main toolbar is now extensible and customizable.

• Overlays: Ability to dock overlays as full-height dynamic panels in the Scene view.

• Package Manager: Added “Export as UPM package” option; added package signing support via CLI.

• Version Control: Added a new Editor Toolbar button for Unity Version Control.

Audio

• Enhanced Audio Foundation: If set to “Enhanced,” a new platform audio foundation is used on Windows/macOS. Expensive operations (enumerating/starting devices) are moved off the main thread to prevent hitches.

🛠️ Complete Improvements List

• 2D: Improved instantiation performance of GameObjects from Tiles; SpriteAtlas previews now packed asynchronously.

• Android: Added HTTP/2 support for UnityWebRequest; added option to force internal storage for persistent files.

• Asset Bundles: Reduced memory usage by sharing duplicated typetrees.

• Editor: Reduced player build times when both Burst and IL2CPP are involved (up to 22% in some cases).

• GI: OpenCL-based GPU lightmapper is now the default for new projects.

• Input System: Reduced latency on Xbox gamepads on Windows by increasing polling frequency.

• Physics: “Reuse Collision Callbacks” is now enabled by default for new projects.

• Profiler: Increased default frame count to 2,000; added Overview feature to Highlights module.

• VFX Graph: Improved CPU performance by reducing internal dereferencing; enabled sticky notes in groups.

Full List of Fixes (6000.3.0f1)

(Below is a curated selection of the most impactful fixes from the full log)

2D & Physics

• Fixed memory regression in Light2D shader.

• Fixed crash in TilemapRenderer when destroyed while graphics renderer is still rendering.

• Fixed issue where RigidBody2Ds could affect shadow caster size.

• Physics: Fixed Multi-box pruning broad phase restored (improves performance in larger worlds).

• Physics: Fixed crash when exiting playmode due to thread-safety issues in physics scene data.

Editor & UI

• Crash Fixes: Fixed crashes related to AssetBundle.UnloadAsync, FBX import with corrupted Blendshapes, and heavy load on macOS Play Mode entry.

• UI Toolkit: Fixed ListView bug where drag operations selected items even with SelectionType.None.

• UI Toolkit: Fixed massive performance issues when adding items via AddItem with rebuildTree set to false.

• IMGUI: Fixed carriage return issues in InputField on Windows.

Graphics (URP/HDRP)

• DX12: Fixed main thread queuing too many frames; fixed performance regressions on specific devices.

• HDRP: Fixed artifacts in deferred lighting after disabling path tracing.

• URP: Fixed SSAO precision issues on Mobile devices; fixed Spotlights with small angles not rendering on mobile.

• Vulkan: Reduced memory overhead for command buffers when using graphics jobs.

Scripting & IL2CPP

• IL2CPP: Fixed random crashes with exit code 139 on macOS arm64.

• IL2CPP: Improved startup time by delaying creation of generic method instances.

• Mono: Fixed crash when attaching a profiler.

• Burst: Fixed crash when scheduling jobs in a constructor due to incorrect Shared Static memory handling.

📉 API Changes

Deprecations

• Multiplayer Widgets package is deprecated in favor of Unity Building Blocks.

• Facebook Instant Games platform is deprecated.

• Cloud Diagnostics is deprecated (migrated to new diagnostics experience).

• Physics: Physics.autoSyncTransforms is deprecated. Use Physics.SyncTransforms instead.

New APIs

• Scripting: Added TransformHandle (Unmanaged access to transform data, Burst compatible).

• Accessibility: Added screen reader support for Container Views, Dropdowns, Tab Buttons, and Text Fields across mobile and desktop.

• Audio: ProcessorInstance, GeneratorInstance, and RootOutputInstance now implement IEquatable.

For the complete documentation and upgrade guides, please visit the official Unity Documentation.