Unity Input System

Unity Input System (new)

Read input through Unity's Input System package (com.unity.inputsystem, 1.x) — action-based, device-agnostic, rebindable. Targets Unity 6.3 LTS. This is the modern replacement for the legacy Input.GetAxis/Input.GetKey Input Manager.

When to use

• Use when setting up movement/jump/fire input, defining an .inputactions asset with action maps and control schemes, wiring a PlayerInput component, reading a Vector2 stick/WASD value, or handling gamepad + keyboard + touch from one set of actions.
• Use when Packages/manifest.json contains com.unity.inputsystem or the project has an *.inputactions asset.

*When not to use: rebindable-control architecture* across engines → input-systems (this skill is the Unity-specific API). Moving the character once you have the input vector → unity-physics / unity-csharp-scripting.

Core workflow

1. Check Active Input Handling (Project Settings → Player). The package only receives input when this is Input System Package (New) or Both. Both is required if any old Input.GetAxis code remains.
2. Create an `.inputactions` asset. Add an action map (e.g. Gameplay), add actions (Move = Value/Vector2, Jump = Button, Fire = Button), and bind them to controls and composite bindings (WASD = 2D Vector composite).
3. Choose how to read it:

• `PlayerInput` component (designer-friendly) — drop it on the player, point it at the asset, pick a Behavior (Send Messages / Broadcast / Invoke Unity Events / Invoke C# Events). Best for single/local-coop players.
• Direct in code (InputActionReference / InputActionAsset) — most control; you Enable() actions and read them. Best for systems and tools.

1. Enable the actions/maps you read. PlayerInput enables its default map automatically; actions you reference yourself must be .Enable()d (and disabled on teardown).
2. Switch action maps for context (gameplay ↔ UI/menu) instead of guarding every handler.
3. Verify with the Input Debugger (Window → Analysis → Input Debugger) to confirm devices and that actions fire.

Patterns

1. PlayerInput with "Send Messages" (handlers on the same GameObject)

using UnityEngine;
using UnityEngine.InputSystem;

// PlayerInput (Behavior = Send Messages) calls On<ActionName>(InputValue) by name.
public class PlayerInputReceiver : MonoBehaviour
{
    private Vector2 _move;

    private void OnMove(InputValue value) => _move = value.Get<Vector2>();   // Move action
    private void OnJump(InputValue value) { if (value.isPressed) Jump(); }   // Button action

    private void Update() { /* drive movement from _move */ }
    private void Jump() { }
}

2. Reading an action directly in code (polling a value)

using UnityEngine;
using UnityEngine.InputSystem;

public class DirectMover : MonoBehaviour
{
    [SerializeField] private InputActionReference moveAction;  // assign the Move action

    private void OnEnable()  => moveAction.action.Enable();    // REQUIRED or it reads zero
    private void OnDisable() => moveAction.action.Disable();

    private void Update()
    {
        Vector2 move = moveAction.action.ReadValue<Vector2>(); // continuous value
        transform.Translate(new Vector3(move.x, 0, move.y) * (5f * Time.deltaTime));
    }
}

3. Event callbacks + switching action maps (gameplay ↔ UI)

[SerializeField] private InputActionAsset actions;

private void OnEnable()
{
    actions.FindAction("Gameplay/Fire").performed += OnFire;  // edge event: fires once
    actions.FindActionMap("Gameplay").Enable();
}
private void OnDisable() => actions.FindAction("Gameplay/Fire").performed -= OnFire;

private void OnFire(InputAction.CallbackContext ctx) => Shoot();  // ctx.ReadValue<T>() if needed

private void OpenPauseMenu()                       // change context, don't sprinkle if-checks
{
    actions.FindActionMap("Gameplay").Disable();
    actions.FindActionMap("UI").Enable();
}
private void Shoot() { }

Pitfalls

• No input at all → either Active Input Handling is still Input Manager (Old), or you forgot to Enable() the action/map. PlayerInput auto-enables; raw InputActions do not.
• `InvalidOperationException` about the old input backend → some script still calls Input.GetAxis/Input.GetKey while Active Input Handling is New. Port it or set Both.
• Buttons read as 0 with `ReadValue` → button presses are edge events; use the performed callback (or WasPressedThisFrame()), not per-frame ReadValue for triggers.
• `Send Messages` handlers never fire → the receiving script must be on the same GameObject as the PlayerInput; Broadcast Messages reaches children too.
• Leaking subscriptions → unsubscribe (-=) in OnDisable; re-subscribing in OnEnable without unsubscribing doubles up handlers.
• Touch/gamepad not detected → enable the matching control scheme and confirm the device in the Input Debugger; the Vector2 composite needs all four bindings set.

References

• For interactive control rebinding (PerformInteractiveRebinding), saving/loading bindings as JSON, and local multiplayer with PlayerInputManager, read references/rebinding.md.
• Primary docs: Unity Manual "Input System" (https://docs.unity3d.com/Manual/com.unity.inputsystem.html).

Related skills

• input-systems — engine-agnostic input architecture (rebinding, buffering, multi-device).
• unity-csharp-scripting — the MonoBehaviour these handlers live in.
• unity-physics — applying the input vector to a Rigidbody.