Common Errors and Fixes In Unity

No matter how experienced you are, errors are a daily part of Unity development. A missing semicolon, a forgotten assignment or a typo can stop your game from running. Once you understand what that error message means, fixing them becomes easy. This article covers the most common Unity errors.

Error 1: NullReferenceException

What it looks like:

NullReferenceException: Object reference not set to an instance of an object.

What it means: You tried to use something that doesn't exist. A variable is null (empty).

Common causes:

• Forgot to assign a variable in Inspector.
• Trying to access a destroyed GameObject.
• Using GetComponent() on something that doesn't have that component.

Example of the problem:

How to fix:

Error 2: MissingReferenceException

What it looks like:

MissingReferenceException: The object of type 'GameObject' has been destroyed.

What it means: The object existed before, but was destroyed. You're still trying to use it.

Example of the problem:

How to fix:

Error 3: IndexOutOfRangeException

What it looks like:

IndexOutOfRangeException: Index was outside the bounds of the array.

What it means: You tried to access array position that doesn't exist. Example: array of size 5, but you tried position 10.

Example of the problem:

How to fix:

Error 4: CS1002 (Missing Semicolon)

What it looks like:

Assets/Scripts/Player.cs(12,25): error CS1002: ; expected.

What it means: You forgot a semicolon ; at the end of a line.

Example of the problem:

How to fix: Add ; at the end of the line.

Most common places to forget:

• End of variable declaration: int score = 0;.
• End of method call: Debug.Log("Hello");.
• End of statement: transform.position = new Vector3(0,0,0).

Error 5: CS0103 (Variable doesn't exist)

What it looks like:

Assets/Scripts/Player.cs(15,13): error CS0103: The name 'healh' does not exist in the current context.

What it means: You typed a variable name wrong (typo). C# is case-sensitive.

Example of the problem:

How to fix: Check spelling. health vs healh. Player vs player.

Common typos:

• Update vs update (U must be capital).
• Start vs start (S must be capital).
• transform vs Transform (lowercase t).