# Device
Some command line arguments perform actions on the device itself while scrcpy is
running.
## Stay awake
To prevent the device from sleeping after a delay **when the device is plugged
in**:
```bash
scrcpy --stay-awake
scrcpy -w
```
The initial state is restored when _scrcpy_ is closed.
If the device is not plugged in (i.e. only connected over TCP/IP),
`--stay-awake` has no effect (this is the Android behavior).
## Turn screen off
It is possible to turn the device screen off while mirroring on start with a
command-line option:
```bash
scrcpy --turn-screen-off
scrcpy -S # short version
```
Or by pressing MOD+o at any time (see
[shortcuts](shortcuts.md)).
To turn it back on, press MOD+Shift+o.
On Android, the `POWER` button always turns the screen on. For convenience, if
`POWER` is sent via _scrcpy_ (via right-click or MOD+p),
it will force to turn the screen off after a small delay (on a best effort
basis). The physical `POWER` button will still cause the screen to be turned on.
It can also be useful to prevent the device from sleeping:
```bash
scrcpy --turn-screen-off --stay-awake
scrcpy -Sw # short version
```
## Show touches
For presentations, it may be useful to show physical touches (on the physical
device). Android exposes this feature in _Developers options_.
_Scrcpy_ provides an option to enable this feature on start and restore the
initial value on exit:
```bash
scrcpy --show-touches
scrcpy -t # short version
```
Note that it only shows _physical_ touches (by a finger on the device).
## Power off on close
To turn the device screen off when closing _scrcpy_:
```bash
scrcpy --power-off-on-close
```
## Power on on start
By default, on start, the device is powered on. To prevent this behavior:
```bash
scrcpy --no-power-on
```
## Start Android app
To list the Android apps installed on the device:
```bash
scrcpy --list-apps
```
An app, selected by its package name, can be launched on start:
```
scrcpy --start-app=org.mozilla.firefox
```
This feature can be used to run an app in a [virtual
display](virtual_display.md):
```
scrcpy --new-display=1920x1080 --start-app=org.videolan.vlc
```
The app can be optionally forced-stop before being started, by adding a `+`
prefix:
```
scrcpy --start-app=+org.mozilla.firefox
```
For convenience, it is also possible to select an app by its name, by adding a
`?` prefix:
```
scrcpy --start-app=?firefox
```
But retrieving app names may take some time (sometimes several seconds), so
passing the package name is recommended.
The `+` and `?` prefixes can be combined (in that order):
```
scrcpy --start-app=+?firefox
```