Why does it say the signal is already connected?

Short answer

A signal can only be connected to the same function once. You connected it twice, usually once in the editor and once in code, or in a function that runs more than once. Pick one place and connect there.

The error

You’ll see something like one of these in the Debugger panel. The signal, node and function names will be your own:

_ready(): Signal 'pressed' is already connected to given callable 'Node(main.gd)::_on_button_pressed' in that object.

_exit_tree(): Attempt to disconnect a nonexistent connection from 'Button'. Signal: 'pressed', callable: 'Node(main.gd)::_on_button_pressed'.

Which cause is it?

What’s happening	Go to
The signal has a green icon next to it in the Node dock, and you also call connect() in code	Connected twice
The connect() line is in _process, a button handler, or a node that is removed and added again	Connecting more than once
The error says nonexistent connection	Disconnecting what was never connected

The example scene

The script is on Main. It listens for the button’s pressed signal.

• MainNode2Dconnects to Button.pressed
  • ButtonButton

Connected twice

There are two ways to connect a signal, and doing both is the most common cause. The first is the editor: select Button, open the Node dock next to the Inspector, double-click pressed and pick _on_button_pressed. Godot then shows a green icon next to the signal. The second is code:

GDScript

main.gd

extends Node2D

func _ready() -> void:
  $Button.pressed.connect(_on_button_pressed)

func _on_button_pressed() -> void:
  print("pressed")

C#

Main.cs

using Godot;

public partial class Main : Node2D
{
    public override void _Ready()
    {
        GetNode<Button>("Button").Pressed += OnButtonPressed;
    }

    private void OnButtonPressed()
    {
        GD.Print("pressed");
    }
}

If the green icon is there and this code is also there, the signal is connected twice and Godot complains at the second one.

Fix: keep one. Code is usually the better choice, because you can read it without clicking through the editor. To remove the editor connection, select Button, open the Node dock, right-click the connection under pressed and choose Disconnect. If you’d rather keep the editor connection, delete the connect() line instead.

Connecting more than once

connect() is not something you do every frame or every time something happens. It’s a one-time setup step. Each of these runs more than once, so the second time through it hits an existing connection:

main.gd

func _process(delta: float) -> void:
  $Button.pressed.connect(_on_button_pressed)

The same thing happens when you connect inside a signal handler, or in the _ready() of a node that you remove_child() and add_child() again, since _ready() only runs once but the connection from the first time is still there.

Fix: connect once, in _ready(). If the connection really might already exist, check first:

GDScript

main.gd

func _ready() -> void:
  if not $Button.pressed.is_connected(_on_button_pressed):
    $Button.pressed.connect(_on_button_pressed)

C#

Main.cs

public override void _Ready()
{
    var button = GetNode<Button>("Button");
    if (!button.IsConnected(Button.SignalName.Pressed, Callable.From(OnButtonPressed)))
        button.Pressed += OnButtonPressed;
}

Disconnecting what was never connected

The second error is the mirror image. disconnect() asks Godot to remove a connection, and it complains if there isn’t one. That happens when the connection was made in the editor rather than in code, when disconnect() runs twice, or when you disconnect in _exit_tree() after the node was already cleaned up.

main.gd

func _exit_tree() -> void:
  $Button.pressed.disconnect(_on_button_pressed)
  if $Button.pressed.is_connected(_on_button_pressed):
    $Button.pressed.disconnect(_on_button_pressed)

Most of the time you don’t need to disconnect at all. When a node is freed, every connection to and from it goes with it. Only disconnect when both nodes keep living and you genuinely want to stop listening.

Still stuck?

Click the error in the Debugger panel and look at the stack trace underneath. It lists the exact line that tried to connect, and the lines that called it, so you can see which path ran twice. If the trace only shows one connect() and the editor shows no green icon, print $Button.pressed.get_connections() in _ready(). It lists every connection on that signal, with the function each one points at, so you can see where the first one came from.

Related

How do I connect a signal in code?The connect() call, lambdas, and passing extra arguments.

Using signalsOfficial step-by-step guide to signals.