Windows 10 periodically changes its build number with every major update. When the Windows 10 was released its build number was 10240 and it was bumped to 10586 after there was a major update in November.
Build number is used to verify that the user’s Windows is up to date in short it is used to see if the update installed is legit or not.
Three ways to know your Windows 10’s build number
NOTE: This method is not useful to check if minor update has been installed or not so make sure that you haven’t turned off Windows Update to automatically get updates for your operating system from Microsoft.
Method 1 of 3
Use about Windows to know the build number
Step 1: In the search box, type Winver.exe and then press enter to open About Windows dialogue.
Step 2: Now next to the Windows 10 version number you can see the build number.
Method 2 of 3
Use Settings to check Windows 10’s build number
Step 1: Open settings app from the start menu or press Windows logo + R key.
Step 2: System > About
Step 3: The number next to OS build is the Windows 10 build number.
Method 3 of 3
Check build number using Command Prompt
Step 1: Open Command Prompt by typing CMD in the start menu start menu and then pressing enter.
Step 2: Now type Systeminfo and then press enter.
Step 3: Build number is displayed next to the OS Version.