How to Get a User's Discord ID
What is a Discord ID?
A Discord ID is a unique string of numbers that Discord uses to identify user accounts. This is important as you can have duplicate names on Discord. These numbers are hidden and we have to turn on Developer Mode to access them.
Enabling Developer Mode
Enabling Developer Mode can be done in a few simple steps.
Navigate to your users setting > Appearance > Advanced > Developer Mode

Retrieving Discord IDs

Find the user you want to retrieve the ID from and right click on their name.
Hover over "Copy ID" and right click.