### Overview

By default, niri will attempt to turn on all connected monitors using their preferred modes.
You can disable or adjust this with `output` sections.

Here's what it looks like with all properties written out:

```
output "eDP-1" {
    // off
    mode "1920x1080@120.030"
    scale 2.0
    transform "90"
    position x=1280 y=0
}

output "HDMI-A-1" {
    // ...settings for HDMI-A-1...
}
```

Outputs are matched by connector name (i.e. `eDP-1`, `HDMI-A-1`) which you can find by running `niri msg outputs`.
Usually, the built-in monitor in laptops will be called `eDP-1`.
Matching by output manufacturer and model is planned, but blocked on Smithay adopting libdisplay-info instead of edid-rs.

### `off`

This flag turns off that output entirely.

```
// Turn off that monitor.
output "HDMI-A-1" {
    off
}
```

### `mode`

Set the monitor resolution and refresh rate.

The format is `<width>x<height>` or `<width>x<height>@<refresh rate>`.
If the refresh rate is omitted, niri will pick the highest refresh rate for the resolution.

If the mode is omitted altogether or doesn't work, niri will try to pick one automatically.

Run `niri msg outputs` while inside a niri instance to list all outputs and their modes.
The refresh rate that you set here must match *exactly*, down to the three decimal digits, to what you see in `niri msg outputs`.

```
// Set a high refresh rate for this monitor.
// High refresh rate monitors tend to use 60 Hz as their preferred mode,
// requiring a manual mode setting.
output "HDMI-A-1" {
    mode "2560x1440@143.912"
}

// Use a lower resolution on the built-in laptop monitor
// (for example, for testing purposes).
output "eDP-1" {
    mode "1280x720"
}
```

### `scale`

Set the scale of the monitor.

This is a floating-point number to enable fractional scaling in the future, but at the moment only integer scale values will work.

```
output "eDP-1" {
    scale 2.0
}
```

### `transform`

Rotate the output counter-clockwise.

Valid values are: `"normal"`, `"90"`, `"180"`, `"270"`, `"flipped"`, `"flipped-90"`, `"flipped-180"` and `"flipped-270"`.
Values with `flipped` additionally flip the output.

```
output "HDMI-A-1" {
    transform "90"
}
```

### `position`

Set the position of the output in the global coordinate space.

This affects directional monitor actions like `focus-monitor-left`, and cursor movement.
The cursor can only move between directly adjacent outputs.

> [!NOTE]
> Output scale and rotation has to be taken into account for positioning: outputs are sized in logical, or scaled, pixels.
> For example, a 3840×2160 output with scale 2.0 will have a logical size of 1920×1080, so to put another output directly adjacent to it on the right, set its x to 1920.
> If the position is unset or results in an overlap, the output is instead placed automatically.

```
output "HDMI-A-1" {
    position x=1280 y=0
}
```

#### Automatic Positioning

Niri repositions outputs from scratch every time the output configuration changes (which includes monitors disconnecting and connecting).
The following algorithm is used for positioning outputs.

1. Collect all connected monitors and their logical sizes.
1. Sort them by their name. This makes it so the automatic positioning does not depend on the order the monitors are connected. This is important because the connection order is non-deterministic at compositor startup.
1. Try to place every output with explicitly configured `position`, in order. If the output overlaps previously placed outputs, place it to the right of all previously placed outputs. In this case, niri will also print a warning.
1. Place every output without explicitly configured `position` by putting it to the right of all previously placed outputs.