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Use Google’s Desktop Head Unit (DHU) with a real Android phone. The DHU emulates the car’s Android Auto head unit on your Windows, macOS, or Linux computer, while the phone runs Android Auto and your app. Install the DHU from Android Studio’s SDK Manager, connect the phone by USB Accessory Mode or ADB tunneling, and exercise the projected app before you drive.
Do not confuse this workflow with testing Android Automotive OS. Automotive OS runs directly in an Automotive Android Virtual Device (AVD) and uses different images, controls, and test assumptions. The correct environment depends on which platform your app targets.
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Android Auto and Android Automotive OS require different test environments
“Android Auto” is a phone-projection system. Your app is installed on a phone, Android Auto runs there, and the car’s head unit displays the approved experience. Google’s Desktop Head Unit reproduces that head unit on your development computer. It does not replace the phone.
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“Android Automotive OS” is an operating system built into a vehicle. An app targeting it runs on the vehicle system itself, so the official emulator route is an Automotive AVD with an Automotive system image in Android Studio’s Android Emulator. That environment can expose simulated vehicle properties and rotary input, but it is not a substitute for the Android Auto phone-projection workflow.
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| What you are testing | Use this environment | What it represents | Phone required? |
|---|---|---|---|
| Android Auto app UI and projection behavior | Desktop Head Unit connected to an Android phone | An Android Auto head unit receiving the phone’s projected app experience | Yes |
| Android Automotive OS app behavior | Android Emulator with an Automotive AVD and Automotive system image | An Automotive OS device profile | No phone for the AVD itself |
| Media-session implementation and media-app behavior | Media Controller Test app plus platform testing | Media-session callbacks and browser behavior, including service startup cases | Depends on the test route |
| OEM, vehicle, or production hardware compatibility | Physical vehicle or an official real-hardware test route | Specific car hardware, firmware, screen, and input behavior | Usually yes for Android Auto |
Google’s testing guidance also points to Android Automotive OS testing on a Pixel Tablet, Firebase Test Lab access to real car hardware, and Google Services interoperability testing. Treat these as additional routes with their own availability and coverage; none should be assumed to cover every vehicle or replace testing on the target hardware.
What you need before installing the Desktop Head Unit
- A development computer running Windows, macOS, or Linux.
- An Android phone running Android 9 (API level 28) or later.
- Your app installed on the phone.
- Android Auto installed on the phone. If the phone runs Android 10 (API level 29) or later, sign in to the Play Store and update Android Auto before the first DHU run.
- A USB data cable that supports data transfer for your phone. A charging-only cable cannot carry the required connection.
- Android Studio and access to its SDK Manager.
- For Linux with DHU 2.x, GLIBC 2.32 or later plus the
libc++1andlibc++abi1libraries.
The phone must be unlocked during initial pairing and while you authorize permissions. Have the first-connection terms ready to accept on the phone; an unaccepted prompt can look like a failed emulator connection.
Install the Desktop Head Unit package
- Open Android Studio.
- Open Tools > SDK Manager.
- Select the SDK Tools tab.
- Select the Android Auto Desktop Head Unit Emulator package and choose Apply or OK to download it.
- Locate the installed files under
SDK_LOCATION/extras/google/auto/. The exact value ofSDK_LOCATIONdepends on your Android SDK installation. - On macOS or Linux, make the DHU binary executable if your system does not already mark it as executable. From the directory containing the binary, use a command such as
chmod +x desktop-head-unit.
Keep the DHU directory available in a terminal so you can run the documented connection commands and inspect any console messages. On Linux, verify the required runtime libraries before troubleshooting the phone connection; a missing library prevents the DHU from starting at all.
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For DHU 2.x, Google recommends USB Accessory Mode. This sends the Android Auto connection over the USB cable between the phone and the development computer.
- Unlock the phone and connect it to the computer with the USB data cable.
- Accept any Android Auto terms, permissions, USB prompts, or trust dialogs shown on the phone.
- Open a terminal in the DHU directory.
- Start the DHU with
./desktop-head-unit --usb. On Windows, use the equivalent executable command for the installed binary. - Wait for the DHU window to display the Android Auto interface, then open the app from the available app launcher or media surface.
If the phone is charging but the DHU does not detect it, charging alone does not prove that the cable supports the required transport. Try a known-good data cable and a different USB port. Keep the phone unlocked while the first connection is established.
Windows USB driver considerations
On Windows, USB Accessory Mode may require a WinUSB driver. The DHU documentation notes that this driver can interfere with ADB. If the phone disappears from ADB after installing or switching the driver, restart ADB and retry. If detection remains unreliable, use the ADB-tunneling route instead of repeatedly changing drivers.
Use ADB tunneling when USB Accessory Mode is unsuitable
ADB tunneling is the documented alternative connection method. It requires Android Auto’s developer mode, the head unit server, and a port forward from the computer.
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- In Android Auto’s developer options, start the head unit server.
- Enable Add new cars to Android Auto. This allows the phone to establish the development connection.
- Connect the phone to the computer by USB and accept the Android debugging authorization prompt. The phone must remain unlocked for authorization.
- On the computer, verify that ADB can see the phone, then create the documented tunnel with
adb forward tcp:5277 tcp:5277. - Launch the DHU from its installation directory using the ADB connection method described in Google’s DHU guide.
ADB tunneling is not just a different launch flag: the Android Auto developer settings and running head unit server are prerequisites. If the tunnel command succeeds but the DHU remains blank, check that the server is still running and that the phone has accepted all first-run prompts.
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Enable Android Auto developer mode safely
Android Auto has developer options in addition to the phone’s general Android developer options. You may need them for ADB tunneling and for development-only settings such as the head unit server.
- Android 10 and later: open Android Auto settings, find the version information area, and use the documented version-tapping action to unlock developer mode. The exact labels can change with Android Auto updates.
- Android 9 and earlier: use the version and permissions area in Android Auto settings, following Google’s version-specific instructions.
- After developer mode is available, open the overflow menu and enter developer settings to start the head unit server and enable the required connection options.
Do not assume that enabling Android’s general USB debugging automatically enables Android Auto’s head unit server. They are separate settings.
Exercise the app inside the DHU
The DHU window is the place to test the projected experience without driving. Start with the same account state, permissions, and data conditions that a first-time user will have, then repeat the test with an existing signed-in user.
Test touch, rotary, and hybrid input
The DHU documentation describes touch, rotary, and hybrid input modes. Touch mode lets you interact with a pointer as you would with a touchscreen head unit. Rotary mode uses keyboard shortcuts and ignores mouse clicks, so a UI that works only when clicked is not ready for a rotary-equipped vehicle. Hybrid mode lets you cover both interaction styles during one test pass.
- Navigate every screen using touch where the target vehicle has a touchscreen.
- Repeat navigation with rotary keyboard controls, including focus movement, selection, back, and scrolling.
- Check that focus order is logical and that no control becomes unreachable without a mouse.
- Exercise long lists, loading states, errors, and empty states rather than testing only the successful content path.
The DHU also supports configurations and headless operation. A configuration can standardize the simulated head-unit setup for a team. Headless mode is useful for scripted smoke tests in continuous integration, but a passing script still represents only the scenarios and input events that the script covers.
Verify the Android Auto projection rules
Confirm that the app appears in the correct Android Auto category and that its templates, navigation depth, text, and actions remain within the platform’s driving-safety constraints. Test rotation or resizing only if the selected DHU configuration supports those characteristics. Check that the app recovers after the phone screen locks and unlocks, after the connection is interrupted and restored, and after Android Auto is restarted.
Media apps need service-startup tests, not just a visible screen
A media app can fail before its Activity ever appears. Google notes that MediaBrowserService may be started when Android Auto is preparing the media surface, when no Activity can be shown, or when the user is not signed in.
- Force-stop the app, then reconnect or restart Android Auto so the media service is started from a cold state.
- Clear the app’s data and repeat the test as a new user. Verify that the service does not crash while waiting for sign-in or configuration.
- Test with no Activity available to launch and confirm that the media browser still returns valid, safe content or a clear unavailable state.
- Use Google’s Media Controller Test app to inspect media-session behavior, transport controls, metadata, playback state, and queue responses.
- Repeat after a process death, network loss, and an interrupted playback session.
These checks are separate from proving that the app icon launches in the DHU. Before Play review, apply the quality criteria for the app’s category and verify the media-specific startup paths that a normal Activity launch will not reveal.
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- Check the Fit Before You Buy: Your car needs factory wired CarPlay for a compatible iPhone (iOS 10 or later), or factory wired Android Auto for a compatible Android phone running Android 11 or later. Connect your phone with a USB data cable first to check that the matching system works. Not for BMW, Tesla, or aftermarket head units. Video playback, screen mirroring are not supported.
When the target is Android Automotive OS, create an Automotive AVD
Use this route only for an app built for Android Automotive OS or for behavior that depends on the Automotive OS device profile.
- Open Android Studio’s Device Manager or AVD Manager.
- Choose to create a new virtual device.
- Select an Automotive hardware profile rather than a phone or tablet profile.
- Choose an Automotive-targeted system image. Select a stable image when your project supports it; preview images may expose newer behavior but are not equivalent to a production vehicle image.
- Finish the AVD, start it, and install the Automotive OS build of your app.
Bundled Automotive profiles differ in screen shape, resolution, input hardware, and configuration. Image and profile availability varies by API level, Play Store inclusion, and whether your Android Studio release offers the item in stable or preview channels. Record the exact API level, image, and profile used for a reproducible test.
Simulate driving and rotary input
Open the Automotive emulator’s extended controls to change vehicle properties. To simulate motion, set the vehicle speed above zero and select a gear other than Park. Selecting Park represents the parked state. Use these controls to verify that your app responds appropriately when driving restrictions apply and when the vehicle is stationary.
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The Automotive emulator also supports rotary input. Test focus movement and selection with the rotary control instead of relying on mouse clicks. These vehicle-state and rotary controls belong to the Automotive OS emulator; they do not turn the DHU into an Automotive OS device.
Compare the routes before choosing one
| Decision question | Choose DHU plus phone | Choose Automotive AVD | Choose real hardware or an additional test service |
|---|---|---|---|
| Where does the app run? | On an Android phone projected through Android Auto | Inside an Automotive OS virtual device | On the intended phone, car, or vehicle system |
| Do you need a phone? | Yes; the DHU does not remove it | No phone is needed for the virtual Automotive OS device | Usually yes for Android Auto; vehicle-specific requirements apply |
| Best for | Android Auto UI smoke tests, navigation, touch, rotary, and projection behavior | Automotive OS layouts, simulated vehicle properties, and rotary behavior | OEM integration, firmware differences, audio routing, connectivity, and final confidence |
| Vehicle-state controls | Not the Automotive OS vehicle-property controls | Speed, gear, and Park can be simulated through extended controls | Actual vehicle state and hardware behavior |
| Coverage guarantee | Does not guarantee behavior in every car | Does not represent every OEM implementation | Depends on the specific hardware and test coverage |
Troubleshoot a DHU connection that does not start
| Symptom | Checks and corrective action |
|---|---|
| DHU opens but shows no phone | Unlock the phone, accept first-connection terms and permissions, confirm Android Auto is installed and updated on Android 10 or later, and try a different USB data cable or port. |
| USB Accessory Mode cannot detect the phone on Windows | Check the WinUSB requirement. Because the driver can interfere with ADB, restart ADB after changing it. If detection remains unreliable, switch to ADB tunneling. |
| ADB forward succeeds but the DHU is blank | Confirm Android Auto developer mode, the head unit server, and Add new cars to Android Auto are enabled. Reconnect the unlocked phone and rerun adb forward tcp:5277 tcp:5277. |
| DHU fails to launch on Linux | Check that the binary is executable and that DHU 2.x requirements—GLIBC 2.32 or later, libc++1, and libc++abi1—are installed. |
| App is installed but does not appear | Verify that the app declares the appropriate Android Auto category and meets that category’s quality requirements. Restart Android Auto after installation and check the app’s eligibility rather than assuming every phone app is projected. |
| Rotary test appears unresponsive | Use the documented keyboard shortcuts in rotary mode. Mouse clicks are ignored by design in that mode. |
These steps come from the documented DHU setup and connection guidance. They are not a guarantee that a particular cable, driver, phone build, or vehicle will behave identically.
What the DHU cannot prove before you use the car
A successful DHU launch proves that your phone, Android Auto installation, app, and selected head-unit simulation can communicate. It does not certify compatibility with every vehicle. Car manufacturers can differ in screen dimensions, touch latency, rotary hardware, audio focus behavior, USB implementation, firmware, and Android Auto integration.
Use the DHU to find app-level defects early, then validate the release on the actual phone models and vehicles you support. If your release depends on a specific OEM feature, steering-wheel control, microphone path, wireless projection mode, or audio route, include that hardware in the final test plan. No simulator result should be described as a universal vehicle guarantee.
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A practical pre-drive test checklist
- Phone runs Android 9 (API 28) or later and Android Auto is current for the phone’s Android version.
- DHU package is installed from Android Studio’s SDK Manager and the host requirements are met.
- Connection was tested with USB Accessory Mode and, where relevant, ADB tunneling.
- First-run terms, permissions, developer settings, and head unit server requirements were completed.
- App was tested from a clean install, an existing account, and a signed-out state.
- Touch, rotary, and hybrid interaction paths were exercised where applicable.
- Loading, empty, offline, error, reconnect, lock/unlock, and process-restart states were checked.
- Media apps were force-stopped or cleared so service-startup paths were tested without an Activity.
- Category-specific Android Auto quality requirements were reviewed before Play submission.
- Automotive OS targets were tested separately in an Automotive AVD, including simulated speed, gear, Park, and rotary input.
- Vehicle-specific features were verified on the intended physical hardware before relying on the app during a drive.
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