Update user appearance settings
Path parameters
User ID, name, or me
Request body
ThemeDark is required when ThemeMode is "sync". In "single" mode an empty value means "preserve the previously persisted slot" rather than "clear the slot", so partial updates that send only one slot keep the other intact.
ThemeLight is required when ThemeMode is "sync". In "single" mode an empty value means "preserve the previously persisted slot" rather than "clear the slot", so partial updates that send only one slot keep the other intact.
Response
OK
Ignored when ThemeMode is "single"
Ignored when ThemeMode is "single"
ThemePreference is the legacy single-field appearance setting. In "single" mode it mirrors the active theme. In "sync" mode modern clients normally mirror the active OS slot, but older clients can update only this field, so it may diverge from ThemeLight or ThemeDark until a modern client saves the full appearance state again.