What Is an SID? (Security Identifier/SID Number) GA S REGULAR Menu Lifewire Tech for Humans Newsletter! Search Close GO Software & Apps > Windows 78 78 people found this article helpful
What Is an SID Number?
Every Windows user has a unique security identifier
By Tim Fisher Tim Fisher Senior Vice President & Group General Manager, Tech & Sustainability Emporia State University Tim Fisher has more than 30 years' of professional technology experience. He's been writing about tech for more than two decades and serves as the VP and General Manager of Lifewire. lifewire's editorial guidelines Updated on December 2, 2020 Tweet Share Email Tweet Share Email Windows The Ultimate Laptop Buying Guide A SID, short for security identifier, is a number used to identify user, group, and computer accounts in Windows. They're created when the account is first made in Windows and no two SIDs on a computer are ever the same. The term security ID is sometimes used in place of SID or security identifier. Why Does Windows Use SIDs
Users (you and me) refer to accounts by the account's name, like "Tim" or "Dad", but Windows uses the SID when dealing with accounts internally. If Windows referred to a common name like we do, instead of a SID, then everything associated with that name would become void or inaccessible if the name were changed in any way. So instead of making it impossible to change the name of your account, the user account is instead tied to an unchangeable string (the SID), which allows the username to change without affecting any of the user's settings. While a username can be changed as many times you like, you're unable to change the SID that's associated with an account without having to manually update all the security settings that were associated with that user to rebuild its identity. Decoding SID Numbers in Windows
All SIDs start with S-1-5-21 but will otherwise be unique. If you need to, you can find a user's security identifier (SID) in Windows for matching users with their SIDs. A few SIDs can be decoded without the instructions linked above. For example, the SID for the Administrator account in Windows always ends in 500. The SID for the Guest account always ends in 501. You'll also find SIDs on every installation of Windows which correspond to certain built-in accounts. For example, the S-1-5-18 SID can be found in any copy of Windows you come across and corresponds to the LocalSystem account, the system account that's loaded in Windows before a user logs on. Here's an example of a user SID: S-1-5-21-1180699209-877415012-3182924384-1004 Yours will be different, but the purpose of each part of the SID remains the same: S 1 5 21-1180699209-877415012-3182924384 1004 Indicates that this is a SID SID specification version number Identifier authority Domain or local computer identifier Relative ID Any group or user that was manually created (i.e., not included in Windows by default) will have a Relative ID of 1000 or greater. The following are a few examples of the string values for groups and special users that are universal across all Windows installs: S-1-0-0 (Null SID): Assigned when the SID value is unknown, or for a group without any members.S-1-1-0 (World): This is a group of every user.S-1-2-0 (Local): This SID is assigned to users who log on to a local terminal. More on SID Numbers
While most discussions about SIDs occurs in the context of advanced security, most mentions on our site revolve around the Windows Registry and how user configuration data is stored in certain registry keys that are named the same as a user's SID. So, in that respect, the above summary is probably all you need to know about SIDs. However, if you're more than casually interested in security identifiers, Microsoft has a full explanation of SIDs. You'll find information about what the various sections of the SID actually mean and you can see a list of well-known security identifiers like the S-1-5-18 SID we mentioned above. SID Used in Other Terms
SID is also an acronym for other technology terms but none of them are related to an SID as it's explained above. Some examples include session identifier, serial interface device, standard integrated desktop, Safer Internet Day, and subscriber identification. The .SID letter group is also used in some file extensions. For example, ScanIt Documents, SID Audio, MrSID Image, and Steam Game Data Backup files all use the SID suffix to indicate their relative file formats. FAQ How do I find my SID in Windows? You can find a user's SID using the Windows Management Instrumentation Command. In Command Prompt, type wmic useraccount where name="USER" get sid replacing USER with the username > Enter. How do you change the SID in Windows? Go to C:\Windows\System32\Sysprep and run sysprep.exe. Select the Generalize checkbox, then select OK. When Sysprep is done, restart the computer. Was this page helpful? Thanks for letting us know! Get the Latest Tech News Delivered Every Day Subscribe Tell us why! Other Not enough details Hard to understand Submit More from Lifewire How to Find a User's Security Identifier (SID) in Windows MDW File (What It Is & How to Open One) How to Change the User Folder Name in Windows 10 What Is a Registry Value? HKEY_USERS (HKU Registry Hive) Task Manager (What It Is & How to Use It) HKEY_CURRENT_USER (HKCU Registry Hive) What Is HKEY_LOCAL_MACHINE? How to Change Another User's Password in Windows How to Map a Network Drive in Windows 11 What Is a File Extension & Why Are They Important? How to Unblock Someone on Instagram How to Change a Login Picture on Mac What Is the Default Windows Password? 6 Best Ways to Search for People on Facebook How to Group Objects in Google Slides Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies