Show sync provider notifications
This DWORD value controls whether File Explorer displays notification banners from sync providers.
since 0.9.8.11
Purpose
Show registry keys (1)
HKU\.DEFAULT\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\ShowSyncProviderNotifications
This DWORD value controls whether File Explorer displays notification banners from sync providers. A value of 0 suppresses these banners. They include OneDrive-related messages and, according to Microsoft, notifications about new Windows features.
The value does not disable a sync provider or stop file synchronization. It controls only the associated messages displayed in File Explorer.
Notes
Additional effects
The same notification area can be used for informational or promotional messages about Microsoft services. Setting the value to 0 also suppresses such banners when they are delivered through this File Explorer mechanism.
Possible side effects
Users no longer see messages delivered through this notification mechanism. Useful notices from a sync provider or information about new File Explorer features may therefore be hidden along with promotional content.
Notes
This entry is an individual per-user File Explorer preference, not a Group Policy value stored in a Policies branch.
The specified HKEY_USERS\.DEFAULT hive is not the default user profile stored under C:\Users\Default. Windows can map HKEY_CURRENT_USER to HKEY_USERS\.DEFAULT when the applicable security context has no user hive loaded. File Explorer running for an interactively signed-in user normally reads that user's own HKEY_USERS\‹SID› branch through HKEY_CURRENT_USER.
Consequently, storing the value only at the path shown above normally does not affect File Explorer for regular signed-in users, nor is it automatically inherited by newly created user profiles. The actual default user profile uses C:\Users\Default\NTUSER.DAT, whose registry hive is not mounted as HKEY_USERS\.DEFAULT.
Microsoft documentation
Microsoft Q&A: Sync notification and feed source
Microsoft Learn: Predefined Keys
Microsoft Learn: Customize the default user profile by using CopyProfile