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

This problem should be fixed in scrcpy v1.22: **update to the latest version**.

On older versions, you must 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

Also, 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 to enable mipmapping:

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


### 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)