Collider2D types (box, circle, polygon) in Unity

Introduction

Colliders in Unity help detect when objects touch or overlap. Different shapes fit different object types better.

Use a BoxCollider2D for square or rectangular objects like crates or doors.

Use a CircleCollider2D for round objects like balls or coins.

Use a PolygonCollider2D for irregular shapes like characters or complex platforms.

Syntax

Unity

AddComponent<BoxCollider2D>()
AddComponent<CircleCollider2D>()
AddComponent<PolygonCollider2D>()

Each collider type is a component you add to a GameObject in Unity.

You can adjust size and shape in the Inspector or by code.

Examples

Adds a box-shaped collider to the object.

Unity

gameObject.AddComponent<BoxCollider2D>();

Adds a circle-shaped collider to the object.

Unity

gameObject.AddComponent<CircleCollider2D>();

Adds a polygon-shaped collider to the object.

Unity

gameObject.AddComponent<PolygonCollider2D>();

Sample Program

This script adds three different 2D colliders to the same GameObject and prints their properties.

Unity

using UnityEngine;

public class ColliderExample : MonoBehaviour
{
    void Start()
    {
        // Add a BoxCollider2D
        var box = gameObject.AddComponent<BoxCollider2D>();
        box.size = new Vector2(2f, 3f);

        // Add a CircleCollider2D
        var circle = gameObject.AddComponent<CircleCollider2D>();
        circle.radius = 1.5f;

        // Add a PolygonCollider2D
        var polygon = gameObject.AddComponent<PolygonCollider2D>();
        polygon.points = new Vector2[] {
            new Vector2(0, 0),
            new Vector2(1, 0),
            new Vector2(1, 1),
            new Vector2(0, 1)
        };

        Debug.Log("Box size: " + box.size);
        Debug.Log("Circle radius: " + circle.radius);
        Debug.Log("Polygon points count: " + polygon.points.Length);
    }
}

Important Notes

PolygonCollider2D lets you define any shape by setting points.

BoxCollider2D and CircleCollider2D are simpler and faster for performance.

You can have multiple Box, Circle, or Polygon colliders on a GameObject if needed for compound shapes.

Summary

BoxCollider2D is best for rectangles and squares.

CircleCollider2D fits round objects.

PolygonCollider2D works for complex shapes by defining points.