WINDOWS SERVICE
OneSyncSvc: Sync Host
A per-user service that synchronizes mail, contacts, calendar and other user data. Windows creates it from a template when you sign in and deletes it when you sign out.
TECHNICAL SUMMARY
| Service name | OneSyncSvc |
|---|---|
| Display name | Sync Host |
| Runs from | C:\Windows\System32\svchost.exe |
| Command line | svchost.exe -k UnistackSvcGroup |
| Runs as | The signed-in user |
| Verdict | Depends on what you use |
| Microsoft, Windows Server 2016 guidance | OK to disable (user service template) |
Paths, signer and service account observed on Windows 11 build 26300 on 12 November 2026. Run the commands below to check your own PC.
Should you touch it?
Depends on what you useMicrosoft states that mail and other applications that depend on this functionality do not work properly when it is not running, and both of its lists rate it OK to disable. If you use apps that sync mail, contacts or calendar through Windows, leave it. On the PC used for this page the instance for the signed-in user was stopped.
What PC Tweaker does with it
PC Tweaker does not change this service. No control in the catalogue stops it, disables it or edits its start type.
Check it yourself
See its state and start type
PowerShellGet-Service OneSyncSvc | Format-List Name, DisplayName, Status, StartType sc qc OneSyncSvcLet it start only when needed (administrator)
Note the START_TYPE that sc qc printed first, so you can put it back.
cmdsc config OneSyncSvc start= demandPut it back
Use the start type you noted.
cmdsc config OneSyncSvc start= <auto|delayed-auto|demand>
Common questions
What does the OneSyncSvc service do?
A per-user service that synchronizes mail, contacts, calendar and other user data. Windows creates it from a template when you sign in and deletes it when you sign out. It runs C:\Windows\System32\svchost.exe (svchost.exe -k UnistackSvcGroup) as The signed-in user.
Can I disable OneSyncSvc?
Depends on what you use. Microsoft states that mail and other applications that depend on this functionality do not work properly when it is not running, and both of its lists rate it OK to disable. If you use apps that sync mail, contacts or calendar through Windows, leave it. On the PC used for this page the instance for the signed-in user was stopped.
Why does the name end in random characters, like OneSyncSvc_67db3c?
Microsoft documents that Windows shows every per-user service as the service name followed by an underscore and a locally unique identifier for the user context. The suffix differs between PCs and sign-ins; it is not a sign of malware.
How do I disable Sync Host the supported way?
Microsoft documents that the templates for per-user services are not shown in the Services console: you change the Start value of the template under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\OneSyncSvc to 4, by policy or script. Windows then still creates the service at sign-in, but stopped and disabled. Do it only if nothing you use syncs mail, contacts or calendar.
How do I check that it is the real service?
On Windows 11 build 26300 the template is registered as svchost.exe -k UnistackSvcGroup and loads C:\Windows\System32\APHostService.dll, signed by Microsoft Windows. sc qc OneSyncSvc prints the template on your PC.