Your Steam Account ID is the number Deadlock uses to identify your matches. The easiest way to find it is to open your Steam profile in a browser and grab the number from the URL (steamcommunity.com/profiles/
7656119...), then paste it into ArcaneStat's onboarding. The app handles the conversion automatically. If you have a custom URL on Steam, use a tool like
steamid.io to look up your numeric ID first.