Your Zwift user ID is something you need for two important purposes: Logging in to ZwiftGPS and signing up at ZwiftPower.
In this post – the first of a series – I show you how to find it in a secure manner using your log file.
Part two will show you how to find it from my.zwift.com.
Part One: The log file holds the truth…
… or at least it contans your Zwift user ID hidden among the many log lines. This makes it very easy to find your user ID. Here are a couple of way to do it without you having to read through the log file yourself.
#1 – on Windows
Copy this line, press Windows+R, paste the line into the Run dialogue, and press Enter:
cmd /k find /i "player id" %UserProfile%\documents\zwift\logs\log.txt
The result is like this:

(You can just close the window when you are done)
#2 – on macOS
Copy this line, paste it into a Terminal window, and press Enter:
grep -i 'player id' ~/Documents/Zwift/Logs/log.txt
The result is like this:

#3 – with help from a web app
The app at https://zwifthacks.com/app/id/ does essentially the same as the searches above, just in a browser. You can drag a log file into the dropzone (look for log.txt in your Documents/Zwift/Logs folder or send it to yourself from the iOS version of Zwift).
In a moment your user ID will be shown:

Coming up: Part Two: Finding your ID on my.zwift.com