AC Unity has native DS4 support with it displaying the DS4 button prompts in game, but only on connecting the DS4 Version 1 controller.
On connecting the newer DS4 Version 2 controller, the game won't load in the DS4 button prompts and will instead load in the Xbox button prompts.

This issue occurs due to the game coded to look only for the version 1 DS4 controller via its device ID and then load the PlayStation button prompts ingame.
The version 2 controller uses a different device ID and because of this different ID, the game doesn't recognise the controller as DS4 and will not load the PlayStation button prompts ingame.

Before proceeding any further with this guide, please connect your DS4 controller with a USB cable.

Open Steam in big picture mode. you can do so by clicking the rectangle button on the top right of the steam application. this button is right between your steam user name and the minimise button.
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This will open your steam library in Big Picture mode and here click on the big LIBRARY button.
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In the Library menu, click on this game and you will be lead to the game's Big picture menu.
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In this menu, go to the Manage Game option and then on the right, click on the Controller Options button.
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In this small menu, click on the Global Setting (PS/Xbox) button and a drop down box will open. here select the Forced Off option.
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Click on the Ok button and then press the Alt F4 button on your keyboard to exit out of the Big Picture mode.

With this we have disabled steam input for this game. now continue to Step 2.

Download the DS4Windows_3.0.10_x64.zip file from this link below:
https://github.com/Ryochan7/DS4Windows/releases/tag/v3.0.10


Extract the zip file into your Documents folder using Winrar or 7Zip software and you will get a folder called DS4Windows.

Go into this folder and open the DS4Windows Application file.

On opening this Application file, you will be presented with a small prompt asking where to save your profile and settings.
Select the Program Folder option and the DS4Windows app will open.

Now you will be prompted with this Driver setup window to install a controller driver.
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Click on the Install ViGEmBus Driver button and an installer window will open.
Tick on the small checkbox near the bottom of the installer window and then click on the Next button.
This will install the Virtual Gamepad Emulation Bus Driver required by DS4Windows and once this driver is installed, click on the Finish button to close the installer.
Scroll down in the Driver setup window and click on the Finish button to close it.

On the bottom right of the DS4Windows application window, click on the Start button.
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Your controller will now appear in DS4Windows
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Click on the Profiles tab
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Click on the Default text and once its selected, click on the Duplicate option.
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You will have to type a name for this Profile. name it as AC Unity and once you are done naming, click on the Save button.
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Now double click on this new AC Unity profile.
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The Profile editor window will now open and here click on the Other tab.
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In here, locate the Emulated Controller text and right next to it click on the Xbox 360 button. then from the small drop down list, select the DualShock 4 option.
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Now click on the Touchpad tab.
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Right next to the Output Mode text, click on the Mouse button.
then from the drop down list, select the Passthru option.
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Click on the Save button and this will lead you back to the Controller section.
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Now click on the Auto Profiles tab.
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In here, click on the Add Programs button
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From the small drop down list, select the Browse for Other Programs option. this should open a window in which you have to navigate to this game's root folder.
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Locate the game's root folder in this new window and this folder is called Assassin's Creed Unity.
Once you are In this folder, double click the ACU Application file.
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This will add the game's exe file in this Auto Profiles list.
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Now on the right side next to the Controller 1 text, click on the (none) button and from the drop down list select the AC Unity profile.
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Click on the Save button and this should ensure that the profile you created is loaded automatically when you launch the game.
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That's it. Minimize the DS4Windows application and continue to step 3.

Download the devreorder_v1.0.3.zip file from this page below:
https://github.com/briankendall/devreorder/releases/tag/v1.0.3


After downloading the zip file, extract it and you should get two folders, and two files.
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Copy the DevLister, and the devreorder files to the Assassin's Creed Unity folder.

Then copy the dinput8.dll file from the x64 folder (which you got by extracting the zip file) to the same Assassin's Creed Unity folder.

It should look like this after copying in the necessary files. (see the selected files in the image)
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Make sure that DS4windows is open and running.
Open the DevLister Application file that you copied into this folder and this application should open and show these two entries which is displayed in this image.
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These two entries that is displayed in this application denote two devices. one is a virtual device and the other is a physical device.

The one listed here as Controller (XBOX 360 For Windows) is the virtual device while the second device "Wireless Controller" is our DS4 v2 controller which is the physical device.

The GUID is the set of words and numbers listed after the device names in the DevLister.exe. this will be different for your PC and won't be same as what is displayed in the image.


Now keeping this DevLister application open, you have to download another software for editing some of the values in the devreorder INI file.

Download and install Notepad++ from the link below:
https://github.com/notepad-plus-plus/notepad-plus-plus/releases/download/v8.2.1/npp.8.2.1.Installer.x64.exe

Come back to the Assassin's Creed Unity folder after Notepad++ is installed.

Right click on the devreorder INI file and select the Edit with Notepad++ option.
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The file will open and this is how it will look.
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In the [order] section and below the ; vjoy Device line, you have to delete these selected lines as seen in this image.
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Type Wireless Controller in the line that is below the ; vjoy Device line.

Then in the next line, you have to paste the device GUID for the Wireless Controller.
If you remember from before, this GUID is seen in the DevLister application and is right next to the Wireless Controller entry.

So select and highlight the GUID that starts from the { symbol with your mouse cursor, then right click and select copy.















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Paste the GUID that you copied from the DevLister application in the next line after the Wireless Controller line that you had typed before.

Make sure there is a empty line after the GUID line and before the [hidden] section. It should look like this in Notepad++ after you are done typing.
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Next in the [hidden] section and below the ; Example: line, you have to delete these selected lines as seen in this image.
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Type Controller (XBOX 360 For Windows) in the line that is below the ; Example: line.

Then in the next line, you have to paste the device GUID for the Controller (XBOX 360 For Windows).
Once again this GUID is seen in the DevLister application and is right next to the Controller (XBOX 360 For Windows) entry.

So select and highlight the GUID that starts from the { symbol with your mouse cursor, then right click and select copy.















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Paste the GUID that you copied from the DevLister application into the next line after the Controller (XBOX 360 For Windows) line that you had typed before.

Make sure there is a empty line after the GUID line and before the [visible] section. It should look like this in Notepad++ after you are done typing.
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Next in the [visible] section and below the ; Example: line, you have to delete these selected lines as seen in this image.
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Right Click and copy these selected lines from the [order] section as seen in this image.
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Right Click paste these selected lines in the [visible] section and below the ; Example: line. this is where you had deleted the lines previously.
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Make sure there is a empty line after GUID line and before the [ignored processes] section. It should look like this in Notepad++ after you are done typing.
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Now press the Ctrl and S keys on your keyboard and this will save the edits that you have made to this devreorder INI file.

And that's it. now close this file and launch the game and the game will now show the PlayStation button prompts for your DualShock 4 version 2 controller.

Creator of the fork for DS4windows
Ryochan7

Creator of Devreorder tool
Brian Kendall