itch.io

I'm far too late to the party but just for future reference: this error message is trying to tell you that the folder where you installed butler is not included in your %PATH% environment variable.

To quote from the manual:

Download butler from https://itchio.itch.io/butler

Extract the downloaded .zip file to a folder of your choice (e.g. C:\butler)

Add that folder to your PATH:

1. Press Win + X and select System
2. Click Advanced system settings
3. Click Environment Variables
4. Under System variables, find and select Path, then click Edit
5. Click New and add the path to the folder where you extracted butler (e.g. C:\butler)
6. Click OK to save all changes

You either forgot the third bullet prompt or did something wrong while doing it.

Also, changes to your PATH will only take effect in command prompt windows you open after doing those changes, not in command prompt windows that were already open before. Just open a new command prompt, or reboot your computer if you want to be sure.

Explanation: When you type something like `butler` into your command prompt, Windows goes through the folders that are listed in your PATH variable to see if any of them contain an executable file called `butler`. If yes, it runs that file, and if no, it throws the error message you've encountered.

(People might come across this post via Google so I think a little thread necromancy is excusable)