Change font size in row based on cell value within specific column

How about this,

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim x As Long
        For x = Range("A" & "20000").End(xlUp).Row To 1 Step -1
                        If Cells(x, 1).Value = 1 Then Application.Rows(x).Font.Bold = True Else: Application.Rows(x).Font.Bold = False
        Next x
        
    End Sub