The Salesforce User ID is the unique identifier for your Salesforce user identity. Use the steps below to find it.

Salesforce Lightning:

  1. Log in to the Salesforce org.
  2. Click the Gear icon available at the top right corner of the screen.
  3. Select Developer Console. The Developer Console window opens.
  4. Go to the Query Editor tab.

  5. Enter any of the following queries and click the Execute button.

    To get all user's ID (18-digit) and Name
    SELECT Id, Name FROM USER
    CODE
    To get specific user ID (18 digit)
    SELECT Id, Name FROM USER
WHERE Name like 'user name'
    CODE

You can see the 18-digit user ID as a result of the respective query.