Swap CUDA Toolkit Versions on Windows

This guide provides two methods for swapping CUDA versions on Windows:

1. Manual method using System Environment Variables (forked from bycloud)
2. Automated method using a PowerShell script (added by me)

Method 1: Manual CUDA Version Swapping

For ease, I will be demonstrating switching from CUDA 11.6 to CUDA 11.3, but the same methods apply to other versions.

Step 0: Check CUDA Version

Check what version of CUDA you have. You can enter this in any command prompt (cmd, anaconda, etc):

nvcc --version

• If you get something like this:

  'nvcc' is not recognized as an internal or external command,
   operable program or batch file.
  

  This means you don't have any CUDA installed. You can download your desired CUDA Toolkit version here (everything default would be fine)

  A quick rule of thumb:

  • NVIDIA GPU >= 30 series --> CUDA 11.0+
  • NVIDIA GPU < 30 series --> CUDA 10.2 (CUDA 10.0 & 10.1 kinda outdated, use 10.2 unless specified)

  You can also check your GPU compatibility here for NVIDIA GPU < 30 series. If your GPU has CC >= 3.7, then it supports PyTorch.

  If you just freshly downloaded CUDA, then you would not need to proceed in the following steps, because you would have the CUDA version you want. You can do another quick check with nvcc --version to check your version in any command prompt.

• If you get something like this:

  

  Then it means you have CUDA installed. And in my case, it's CUDA 11.6. I will be swapping to CUDA 11.3 in the following steps.

Step 1: Locate System Environment Variables

Open up your environment variables. You can search "env" in the search tab, it should look something like this.

Then open it. Then click "Environment Variables"

Then it should open up a window like this

Step 2: Change System Variables

Double check on CUDA_PATH and this window should pop up

Then enter the target version of your CUDA there. In my case it's changing 11.6 to 11.3

Press ok and proceed to the next step.

Step 3: Change System Paths

Scroll down and find Path, double click to open

You should see your current version on the very top. You're going to have to move your desired version to the very top

So it should look like this after moving

Press ok and you may now close all the windows for environment variables & system properties.

Step 4: Check if succeed

Close the last command prompt, and open a new one. Enter the following command:

nvcc --version

If it outputs your desired version, then you have succeeded in swapping CUDA version.

Method 2: Automated CUDA Version Swapping using PowerShell Script

For a more convenient and automated approach, you can use the provided PowerShell script to switch between CUDA versions.

How to Use the Script

1. Save the script as Switch-CUDAVersion.ps1 in a known location on your computer.
2. Open PowerShell as an administrator.
3. Navigate to the directory containing the script.
4. Run the script using one of the following methods:

Interactive Mode

.\Switch-CUDAVersion.ps1

This will list all available CUDA versions and prompt you to choose one.

Switching to a Specific Version

.\Switch-CUDAVersion.ps1 -Version v12.4

This will switch to CUDA version 12.4 if it's installed.

Listing All Installed CUDA Versions

.\Switch-CUDAVersion.ps1 -ListVersions

This will display a list of all installed CUDA versions.

Getting the Current CUDA Version

.\Switch-CUDAVersion.ps1 -GetCurrent

This will show the currently active CUDA version.

Script Features

• Automatically detects installed CUDA versions
• Allows switching to a specific version
• Updates both CUDA_PATH and Path environment variables
• Can be run interactively or with command-line parameters
• Suitable for inclusion in other scripts or automation workflows

Note

After running the script, you may need to restart any open command prompts or applications for the changes to take effect.