Install on Pixel 4a

From a MacOS computer

Install / Pixel 4a / MacOS


Prepare your Android device

There are a few things you must do to prepare your device to accept a new operating system:

Remove SIM card

On brand new devices, especially those obtained from a carrier, it’s better to remove the SIM card from the device before starting it for the first time, to help with the “OEM Unlocking” step below.

Enable Developer Options

SettingsAbout Phone → tap Build number 7 times

Enable USB debugging

SettingsSystemAdvancedDeveloper OptionsUSB Debugging

Enable OEM Unlocking

SettingsSystemAdvancedDeveloper OptionsOEM unlocking

This step might fail if there is no internet connection. In that case, connect to a WiFi network and then try again.

Prepare your host computer

MacOS Settings

As a safety measure, your computer probably has Gategeeker enabled in order to prevent you from running unknown software like device-flasher.

In order to continue with the installation, you may have to temporarily disable Gatekeeper. See How to open an app that hasn’t been notarized or is from an unidentified developer for more information.

Installation from the M1 Macs is currently not supported due to an incompatibility with the fastboot tool used for flashing and the ARM64 M1 Macs. Intel Macs should work fine.

Download device-flasher

Download device-flasher.darwin

Save this executable to a new directory, where you will also later save the CalyxOS image.

Verify Digest

This is an optional step, useful for ensuring you have the correct device-flasher executable. Open a terminal on your host computer, change to the directory where you saved device-flasher, and then run:

shasum -a 256 device-flasher.darwin

And ensure the result says fab94514f8af55a8d44e984b2a78e785c2b3d76398b108067bf70c98bfbbfa15. This is the unique digest of the device-flasher. If it doesn’t match, then you have a corrupted or incorrect file.

Download factory image

Download CalyxOS Image

Save this image in the same directory as device-flasher. This image will only work for Pixel 4a (sunfish). Any attempt to install this image on a different device model may brick (destroy) the Android device.

Do not extract or rename the zip, simply copy it as-is.

Once downloaded, the next step is to verify the image. This step is optional, but verification helps ensure that you downloaded the image correctly, and that you got the correct image.

Verify Digest

To verify the image, open a terminal window on the host computer where you saved the image and run the command:

shasum -a 256

And ensure the result says 5bc230e7aab78b03c9c1d80178553d4748ef6692377c5f0cb060cf5b1126930d. This is the unique digest of the image file. If it doesn’t match, then you have a corrupted or incorrect file.

Verify Signature

For the highest level of confidence, you can optionally download the signature file and then verify image signature.

Install CalyxOS

Run device-flasher

Now you are ready to install. Ensure that both the CalyxOS image and device-flasher are in the same directory.

Step 1. Connect the USB cable between the computer and the Android device.

Step 2. Run device-flasher

Open a terminal, change to the directory with the firmware image, and run:

chmod +x device-flasher.darwin

Unlock the bootloader

At some point in the installation process, it will ask you to unlock the bootloader.

NOTE: if the bootloader is already unlocked, you will not see the unlock bootloader menu and installation will proceed automatically without you needing to touch anything.

The bootloader unlock menu looks like this:

Press a volume key to select UNLOCK THE BOOTLOADER option. Then press the power key to activate that option.


Once device-flasher is finished, you should now have a fully functional CalyxOS device. If not, please see our Community page for where you can post your questions.


Error running device-flasher

If you get a mysterious error when running device-flasher, or if device-flasher hangs, it may be a USB problem. Try connecting to a different USB port on your computer (yes, not all USB ports are created equal) or a different USB cable.

How do I tell if the bootloader is locked?

In Fastboot “Device State: locked” means the bootloader is locked.

On the initial boot screen, you may also see this if the bootloader is unlocked:

The bootloader is unlocked and software integrity cannot be guaranteed. Any data stored on the device may be available to attackers. Do not store sensitive data on the device.

Back to Stock

If you would like to return to the default operating system, please see Back to Stock Android.

Security Notes

  • Over-the-air Updates: CalyxOS updates are delivered over-the-air (OTA) automatically, without any manual intervention needed. However, if you'd like to manually update your CalyxOS install, see OTA.
  • Security Updates: The Pixel Fold, Tablet, 7a, 7 Pro, 7, 6a, 6 Pro, 6, 5a (5G), 4a (5G), 5 contain the full security patch, as they are still being updated by Google.
  • Security Updates: The Fairphone 4 stock OS follows a different security update release schedule, which usually lags behind by a month or two compared to Pixels. The CalyxOS releases for it only contain the latest fixes to the open source components, such as the OS code and the Linux kernel. Proprietary components such as the bootloader, modem firmware, and other firmware get updates as soon as the stock OS update is available.
  • End-of-life: The Pixel 4a, 4 XL, 4, 3a XL, 3a, 3 XL, 3 are no longer being updated by Google, so the CalyxOS releases for these devices only contain the fixes to the open source components, such as the OS code and the Linux kernel. Proprietary components such as the bootloader, modem firmware, and other firmware no longer get updates.