To find your SteamID64, use the Steam client's Account Details for a direct number, or enable the URL bar in Settings and view your profile - it's a unique 17-digit number used for linking accounts and in some games, often found in your profile URL or easily revealed by removing a custom URL.
Method 1: Account Details (Easiest)
Open the Steam client and click your username in the top-right corner.
Select Account Details from the dropdown.
Your SteamID64 will be listed under your profile name at the top.
Method 2: Browser URL
In Steam, click your username and select Profile.
Click Edit Profile on the right.
Temporarily clear the text in the Custom URL box and click Save.
Your SteamID64 will appear in the address bar of your browser as a 17-digit number.
Method 3: Using a SteamID Finder Website
Go to your Steam profile (either in the client or browser) and copy the entire profile URL.
Visit a SteamID lookup site like STEAMID I/O:
https://steamid.io/lookup
or SteamDB: https://steamdb.info/calculator/
Paste your profile URL into the search bar to get your SteamID64 and also other formats.