A maintained collection of useful & free unity scripts / library's / plugins and extensions.

If you want to suggest a link, then read the Contribution Guidelines first. Please report broken links, outdated assets and spelling mistakes. The links are in no particular order.

Navigation:

• GameObjects & Transforms
• Movement & Animation
• Controls & Input
• Character Controller
• AI & Pathfinding
• Physics
• Particles
• Meshes & Construction
• Materials & Shading
• 2D
• Networking
• VR
• Sound & Music
• UI
• Post-Processing & Rendering
• Mobile
• Debug
• Editor
  • Tools
  • Editors
  • Inspector Extensions
  • Importer
• Serialization & Web
• Social SDKs
• API Extensions & Helper
• Design Patterns
• Other

• RecyclerKit - pooling system
• UnityOctree - octrees
• In-Game Replay System - record and replay transforms

• List View Framework - create dynamic, scrollable lists
• Reaktion - audio reaction toolkit
• DOTween - tween engine
• UnitySpritesAndBones - skeletal sprite animations
• spine-unity - import spine animations

• InputManager - a powerful input manager
• TouchScript - multitouch library

• Unity 2D Platformer Controller - 2d platformer character controller
• CharacterController2D - 2d character controller
• SuperCharacterController - 3d character controller

• A Star Pathfinding for Platformers - A* for platformers
• AStart - basic A* pathfinding
• Astar for Unity - A* pathfinding
• A* Pathfinding Project - A* pathfinding
• UnitySteer - steering, obstacle avoidance and path following behaviors

• Mario Galaxy Gravity for Unity - mario galaxy gravity
• Ocean Community Next Gen - water physics/shader

• KvantSpray - gpu accelerated particles
• NVIDIA Hair Works Integration - Nvidia hair works

• ProceduralToolkit - procedural mesh toolkit/generator
• Draw - draws primitives with lines
• VolumetricLinesUnity - volumetric lines
• giles - 3d runtime level editor
• Voxelmetric - voxel framework
• Procedural Shapes for Unity - procedural shapes
• ICO Sphere Mesh Creator - procedural ico spheres
• Vertex Painter - paint information onto vertices
• FacePaint - paint triangles of meshes
• Simplygon - mesh optimization & lod generation
• TextMesh Pro - generate text with custom styling

• Projects by RM - wet surface & skin shader
• Ocean Community Next Gen - water physics/shader
• Flow Map Shader - flow map shader working with sprites
• VertexPaint - additional vertex streams
• ShaderProject - shader collection
• Skybox Plus - a collection of skybox shaders
• Outline Shader - outline shader which accomodates screen width and camera distance
• Unity Sprite Uber Shader - 3D shading for sprites (e.g. normal mapping)

• UnitySVG - svg renderer
• UnityStbEasyFont - text mesh generator
• SpriteLightKit - 2d sprite lights
• 2D Light of Sight Unity - 2d flat geometric lightning
• Unity Sprite Uber Shader - 3D shading for sprites (e.g. normal mapping)
• Fungus - 2d interactive storytelling game framework
• PolyMesh - 2d shape editor
• Unity Tilemap - 2D tilemap editor

• UNet Authoritative Networking - authoritative networking implementation

• SteamVR - VR SDK
• The Lab Renderer - VR renderer by Valve
• VRTK - contains useful scripts for building VR games
• NewtonVR - VR physics and interactions
• Cutie Keys - VR keyboard

• usfxr - procedual audio effects
• Reaktion - audio reaction toolkit (mac only)
• DefaultMicrophone - gets the default microphone (windows only)

• Unity UI Extensions - collection of ui extensions
• Book Page Curl - page curl transition
• Open Pause Menu - read-to-use pause menu
• Lunar Mobile Console - debug console for mobiles
• InfinityScroll - infinite scrollrects
• TextMesh Pro - generate text with custom styling

• kode80SSR - screen-space reflections
• KinoObscurance - screen-space ambient obscurance
• SMAA - subpixel morphological anti-aliasing
• Temporal Reprojection Anti-Aliasing - anti-aliasing solution used in INSIDE
• kode80CloudsUnity3D - realtime volumetric clouds
• PixelRenderUnity3D - pixelized rendering
• PixelCamera2D - pixel-perfect rendering
• KinoMotion - motion blur using motion vectors
• KinoContour - edge detection
• KinoMirror - kaleidoscope effect
• KinoFringe - chromatic aberration
• KinoBinary - 1-bit monochrome effect
• KinoFeedback - retro framebuffer feedback effect
• KinoRamp - color ramp overlay
• KinoSlitscan - slit-scan effect
• KinoGlitch - glitch effect
• KinoDatamosh - datamosh
• unity vhsglitch - vhs glitch effect
• Scanline Shader - scanline effect
• KinoFog - global fog
• KinoBloom - bloom
• KinoBokeh - bokeh effect
• KinoVignette - vignette
• KinoVision - frame information visualizer
• Unity5Effects - post-processing collection
• LightShafts - light shafts
• VolumetricLights - volumetric lights
• SonarFx - wave patterns
• Cinematic Image Effects - cinematic image effects
• Post-processing Stack - multiple image effects in one pipeline
• Moments - gif recorder
• uDesktopDuplication - realtime screen capture as Texture2D
• Heat Distortion Effect - a shader which distorts the image behind, using a normal map

• Toast - android toast notifications
• FBSucks - android share image & text
• UnityShowAndroidStatusBar - android show statusbar
• Google VR SDK - google mobile vr sdk
• Unity Webview - webview overlay
• CUDLR - remote debugging and logging console
• Simplygon - mesh optimization & lod generation

• uREPL - runtime evaluation of c# expressions
• UberLogger - advanced logging API, improved editor console & ingame console

• REX Diagnostics - runtime evaluation of c# expressions
• Better Defines - platform dependent preprocessor directive manager
• Unity File Debug - enhanced logging
• MissingReferencesUnity - find missing references
• Unity Resource Checker - resource analyzer
• Compile Time Tracker - compile time tracker
• UnityStudio - unity asset export tool
• Screen Shooter - takes screenshots with multiple resolutions at once
• Script Templates for Unity - script templates
• Unity 2D Destruction - sprite destruction
• CurveTexture - bake curves into texture
• Unity3D Rainbow Folders - folder icons
• Unity Themes - editor themes
• Tree Randomizer - randomize unity trees
• Render Settings Duplicator - clones the render settings from one scene to another
• Piviot Transform Helper - adds piviot creation shortcuts to the context menu
• ScriptExecutionOrder Attribute - attribute to specify execution order

• Brainiac - behaviour tree & (behaviour-)node-based visual editor
• Node Editor - (calculation-)node editor
• BrotherhoodOfNode - (more graphical-)node editor for visual things
• VisualNoiseDesigner - visual noise designer
• SimpleGeo - simple geometry painter
• Curves and Splines - curve & spline editor
• Unity 2D Joint Editors - 2d joint editors
• PolyMesh - 2d shape editor
• VertexPaint - vertex data painter
• SabreCSG - a set of level design tools for building complex levels
• Constants Generator Kit - generates static classes for layers, scenes, tags and resources
• Unity Tilemap - 2D tilemap editor

• Reorderable Lists - reorderable list field
• Ordered Dictionary - ordered dictionary field
• ClassTypeReference - class type reference field
• Unity3D ExtendedEvent - extended event selector
• Property Drawer Collection - collection of property drawers
• Node Inspector - node based inspector
• ColorBands - color bands
• QuickEvent - persistent event handlers with static or dynamic values
• Reorder Components - reorder components on your GameObjects

• Unity Excel Importer Maker - excel
• Unity Psd Importer - advanced psd import

• Full Serializer - custom serializer
• Json.Net - Newtonsoft Json.NET
• SQLite4Unity3d - sql lite
• UnityHTTP - http library

• Google Analytics Plugin - Google Analytics
• Google Play Games Plugin - Google Play plugin
• Facebook SDK - Facebook sdk
• Reign Unity Plugin - unified mobile api
• GetSocial SDK - community api
• SOOMLA Framework - store api
• Steamworks.NET - c# wrapper for valve's Steamworks API
• Facepunch.Steamworks - Steamworks C# API (not all features implemented, but better API)

• Camera Extension - a better way of manipulating the culling mask
• Download Manager - simple file downloads
• UnityMainThreadDispatcher - main thread dispatcher
• UnityBitmapDrawing - texture2d drawing extensions
• Unity3D ComponentAttribute - auto component referencing
• Unity3D ExecutionOrderAttribute - execution order attribute
• LINQ to GameObject for Unity - gameobject linq querys
• Chained Works - coroutine chained procedures
• TeaTime - timer queue for coroutines
• Smart Tags and Layers - generates static values for your tags and layers

• Unity Singleton MonoBehaviour - powerful singleton
• Signals - simple event/signal system
• Unity3d Finite State Machine - simple finite stata machine
• stateless - more complex state machines
• Design Patterns in Unity Example - collection of design patterns
• Entitas CSharp - entity component system framework
• strangeioc - inversion of control framework
• Zenject - depedency injection framework
• UniRx - unity reactive extensions implementation

• Unity Right Click - windows context menu extension: 'open with unity'
• No Hot-Reload - prevent unity hot-reloads
• Unity Decompiled - unity 5.3 decompiled
• Unity C# 5.0 and 6.0 Integration - c# 5 & 6 integration for unity
• FLUnity - flash to unity
• Projeny - project management
• CUDLR - remote debugging and logging console
• WebGL - Simple Loading Fix - custom loading bar for the webgl loader
• UtilityKit - SerializationUtil, SpriteAnimator, SpriteAnimator, MathHeloers, AutoSnap, ...
• Remove Boo.Lang and UnityScript Hints - Project Generation Hook to remove references to Boo.Lang and UnityScript assemblies
• Asset Store Batch Mode - API for uploading Unity Asset Store packages
• Unity Size Explorer - analyzes the disk space usage of your build