scrcpy/FAQ.md

# Frequently Asked Questions

[Read in another language](#translations)

Here are the common reported problems and their status.


## `adb` issues

`scrcpy` execute `adb` commands to initialize the connection with the device. If
`adb` fails, then scrcpy will not work.

In that case, it will print this error:

>     ERROR: "adb get-serialno" returned with value 1

This is typically not a bug in _scrcpy_, but a problem in your environment.

To find out the cause, execute:

```bash
adb devices
```

### `adb` not found

You need `adb` accessible from your `PATH`.

On Windows, the current directory is in your `PATH`, and `adb.exe` is included
in the release, so it should work out-of-the-box.


### Device unauthorized


>     error: device unauthorized.
>     This adb server's $ADB_VENDOR_KEYS is not set
>     Try 'adb kill-server' if that seems wrong.
>     Otherwise check for a confirmation dialog on your device.

When connecting, a popup should open on the device. You must authorize USB
debugging.

If it does not open, check [stackoverflow][device-unauthorized].

[device-unauthorized]: https://stackoverflow.com/questions/23081263/adb-android-device-unauthorized


### Device not detected

>     error: no devices/emulators found

Check that you correctly enabled [adb debugging][enable-adb].

If your device is not detected, you may need some [drivers] (on Windows). There is a separate [USB driver for Google devices][google-usb-driver].

[enable-adb]: https://developer.android.com/studio/command-line/adb.html#Enabling
[drivers]: https://developer.android.com/studio/run/oem-usb.html
[google-usb-driver]: https://developer.android.com/studio/run/win-usb


### Several devices connected

If several devices are connected, you will encounter this error:

>     error: more than one device/emulator

the identifier of the device you want to mirror must be provided:

```bash
scrcpy -s 01234567890abcdef
```

Note that if your device is connected over TCP/IP, you might get this message:

>     adb: error: more than one device/emulator
>     ERROR: "adb reverse" returned with value 1
>     WARN: 'adb reverse' failed, fallback to 'adb forward'

This is expected (due to a bug on old Android versions, see [#5]), but in that
case, scrcpy fallbacks to a different method, which should work.

[#5]: https://github.com/Genymobile/scrcpy/issues/5


### Conflicts between adb versions

>     adb server version (41) doesn't match this client (39); killing...

This error occurs when you use several `adb` versions simultaneously. You must
find the program using a different `adb` version, and use the same `adb` version
everywhere.

You could overwrite the `adb` binary in the other program, or ask _scrcpy_ to
use a specific `adb` binary, by setting the `ADB` environment variable:

```bash
set ADB=/path/to/your/adb
scrcpy
```


### Device disconnected

If _scrcpy_ stops itself with the warning "Device disconnected", then the
`adb` connection has been closed.

Try with another USB cable or plug it into another USB port. See [#281] and
[#283].

[#281]: https://github.com/Genymobile/scrcpy/issues/281
[#283]: https://github.com/Genymobile/scrcpy/issues/283



## Control issues

### Mouse and keyboard do not work

On some devices, you may need to enable an option to allow [simulating input].
In developer options, enable:

> **USB debugging (Security settings)**  
> _Allow granting permissions and simulating input via USB debugging_

[simulating input]: https://github.com/Genymobile/scrcpy/issues/70#issuecomment-373286323


### Special characters do not work

The default text injection method is [limited to ASCII characters][text-input].
A trick allows to also inject some [accented characters][accented-characters],
but that's all. See [#37].

Since scrcpy v1.20 on Linux, it is possible to simulate a [physical
keyboard][hid] (HID).

[text-input]: https://github.com/Genymobile/scrcpy/issues?q=is%3Aopen+is%3Aissue+label%3Aunicode
[accented-characters]: https://blog.rom1v.com/2018/03/introducing-scrcpy/#handle-accented-characters
[#37]: https://github.com/Genymobile/scrcpy/issues/37
[hid]: README.md#physical-keyboard-simulation-hid


## Client issues

### The quality is low

If the definition of your client window is smaller than that of your device
screen, then you might get poor quality, especially visible on text (see [#40]).

[#40]: https://github.com/Genymobile/scrcpy/issues/40

To improve downscaling quality, trilinear filtering is enabled automatically
if the renderer is OpenGL and if it supports mipmapping.

On Windows, you might want to force OpenGL:

```
scrcpy --render-driver=opengl
```

You may also need to configure the [scaling behavior]:

> `scrcpy.exe` > Properties > Compatibility > Change high DPI settings >
> Override high DPI scaling behavior > Scaling performed by: _Application_.

[scaling behavior]: https://github.com/Genymobile/scrcpy/issues/40#issuecomment-424466723


### Issue with Wayland

By default, SDL uses x11 on Linux. The [video driver] can be changed via the
`SDL_VIDEODRIVER` environment variable:

[video driver]: https://wiki.libsdl.org/FAQUsingSDL#how_do_i_choose_a_specific_video_driver

```bash
export SDL_VIDEODRIVER=wayland
scrcpy
```

On some distributions (at least Fedora), the package `libdecor` must be
installed manually.

See issues [#2554] and [#2559].

[#2554]: https://github.com/Genymobile/scrcpy/issues/2554
[#2559]: https://github.com/Genymobile/scrcpy/issues/2559


### KWin compositor crashes

On Plasma Desktop, compositor is disabled while _scrcpy_ is running.

As a workaround, [disable "Block compositing"][kwin].

[kwin]: https://github.com/Genymobile/scrcpy/issues/114#issuecomment-378778613


## Crashes

### Exception

There may be many reasons. One common cause is that the hardware encoder of your
device is not able to encode at the given definition:

> ```
> ERROR: Exception on thread Thread[main,5,main]
> android.media.MediaCodec$CodecException: Error 0xfffffc0e
> ...
> Exit due to uncaughtException in main thread:
> ERROR: Could not open video stream
> INFO: Initial texture: 1080x2336
> ```

or

> ```
> ERROR: Exception on thread Thread[main,5,main]
> java.lang.IllegalStateException
>         at android.media.MediaCodec.native_dequeueOutputBuffer(Native Method)
> ```

Just try with a lower definition:

```
scrcpy -m 1920
scrcpy -m 1024
scrcpy -m 800
```

Since scrcpy v1.22, scrcpy automatically tries again with a lower definition
before failing. This behavior can be disabled with `--no-downsize-on-error`.

You could also try another [encoder](README.md#encoder).


If you encounter this exception on Android 12, then just upgrade to scrcpy >=
1.18 (see [#2129]):

```
> ERROR: Exception on thread Thread[main,5,main]
java.lang.AssertionError: java.lang.reflect.InvocationTargetException
    at com.genymobile.scrcpy.wrappers.SurfaceControl.setDisplaySurface(SurfaceControl.java:75)
    ...
Caused by: java.lang.reflect.InvocationTargetException
    at java.lang.reflect.Method.invoke(Native Method)
    at com.genymobile.scrcpy.wrappers.SurfaceControl.setDisplaySurface(SurfaceControl.java:73)
    ... 7 more
Caused by: java.lang.IllegalArgumentException: displayToken must not be null
    at android.view.SurfaceControl$Transaction.setDisplaySurface(SurfaceControl.java:3067)
    at android.view.SurfaceControl.setDisplaySurface(SurfaceControl.java:2147)
    ... 9 more
```

[#2129]: https://github.com/Genymobile/scrcpy/issues/2129


## Command line on Windows

Since v1.22, a "shortcut" has been added to directly open a terminal in the
scrcpy directory. Double-click on `open_a_terminal_here.bat`, then type your
command. For example:

```
scrcpy --record file.mkv
```

You could also open a terminal and go to the scrcpy folder manually:

 1. Press <kbd>Windows</kbd>+<kbd>r</kbd>, this opens a dialog box.
 2. Type `cmd` and press <kbd>Enter</kbd>, this opens a terminal.
 3. Go to your _scrcpy_ directory, by typing (adapt the path):

    ```bat
    cd C:\Users\user\Downloads\scrcpy-win64-xxx
    ```

    and press <kbd>Enter</kbd>
 4. Type your command. For example:

    ```bat
    scrcpy --record file.mkv
    ```

If you plan to always use the same arguments, create a file `myscrcpy.bat`
(enable [show file extensions] to avoid confusion) in the `scrcpy` directory,
containing your command. For example:

```bat
scrcpy --prefer-text --turn-screen-off --stay-awake
```

Then just double-click on that file.

You could also edit (a copy of) `scrcpy-console.bat` or `scrcpy-noconsole.vbs`
to add some arguments.

[show file extensions]: https://www.howtogeek.com/205086/beginner-how-to-make-windows-show-file-extensions/


## Translations

This FAQ is available in other languages:

 - [Italiano (Italiano, `it`) - v1.19](FAQ.it.md)
 - [한국어 (Korean, `ko`) - v1.11](FAQ.ko.md)
 - [简体中文 (Simplified Chinese, `zh-Hans`) - v1.22](FAQ.zh-Hans.md)