There are many reasons why you might want to find the security identifier (SID) for a particular user's account in Windows but in my corner of the world, the common reason for doing so is to determine which key under HKEY_USERS in the Windows Registry to look for user-specific registry data for.
Note: See How To Find User's SIDs in the Registry further down the page for instructions on matching a user name to an SID via information in the Windows Registry, an alternative method to using WMIC. The wmic command didn't exist before Windows XP so you'll have to use the registry method in those older versions of Windows.
How To Find User's SIDs with WMIC
Follow these easy steps to display a table of user names and their corresponding SIDs:
Time Required: It'll take less than a minute to find a user's SID in Windows via WMIC:
Open Command Prompt.
Once Command Prompt is open, type the following command exactly as shown here, including spaces or lack thereof:
wmic useraccount get name,sid
and then press Enter.
You should see a table, similar to the following, displayed in the Command Prompt window:
Name SID Administrator S-1-5-21-1180699209-877415012-3182924384-500 Guest S-1-5-21-1180699209-877415012-3182924384-501 HomeGroupUser$ S-1-5-21-1180699209-877415012-3182924384-1002 Tim S-1-5-21-1180699209-877415012-3182924384-1004 UpdatusUser S-1-5-21-1180699209-877415012-3182924384-1007
This is a list of each user account in Windows, listed by user name, followed by the account's corresponding SID.
Now that you're confident that a particular user name corresponds to a particular SID, you can make whatever changes you need to in the registry or do whatever else you needed this information for.
How To Find User's SIDs in the Registry
You can also determine a user's SID by looking through the ProfileImagePath values in each S-1-5-21 prefixed SID listed under the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList key.
The ProfileImagePath value within each SID-named registry key lists the profile directory, which includes the user name.
For example, the ProfileImagePath value under the S-1-5-21-1180699209-877415012-3182924384-1004 key on my computer is C:\Users\Tim so I know that the SID for the user "Tim" is "S-1-5-21-1180699209-877415012-3182924384-1004".
Note: This method of matching users to SIDs will only show those users who are logged in or have logged in and switched users. To continue to use the registry method for determining other user's SIDs, you'll need to log in as each user on the system and repeat these steps. This is a big drawback so, assuming you're able, you're much better off using the wmic command method above.