Compare two sheets and highlight unmatched rows or copy to new sheet

[Fatman003]

I want to match rows from two different sheets and put the unmatched rows into another Sheet3 or it should just highlight in the first column of the unmatched row (depending on the easier method). The code should compare the rows of the two Sheets and copy the outstanding rows into a newly created sheet. Sheet2 (say Jan 2020) contains more rows than Sheet1 (Dec 2019) as its the recently updated sheets and they both contain rows of over 22 thousand with both having unique ID as the first column.

My below code tries to highlight all the unmatching cells and takes longer time to finish. So one of the fastest way is for it to just highlight the first column of the rows or copy the row into a new sheet.

Sub RunCompare()
Call compareSheets("Sheet1", "Sheet2")
End Sub

Sub compareSheets(shtSheet1 As String, shtSheet2 As String)
Dim c As Integer, j As Integer, i As Integer, mydiffs As Integer, cnt1 As Integer, cnt2 As Integer
Dim noexist As Integer
cnt2 = Worksheets("Sheet2").Cells.SpecialCells(xlCellTypeLastCell).Row
cnt1 = Worksheets("Sheet1").Cells.SpecialCells(xlCellTypeLastCell).Row
'For each cell in sheet2 that is not the same in Sheet1, color it yellow
For i = 1 To cnt2
    For j = 1 To cnt1
        If ActiveWorkbook.Worksheets(shtSheet2).Cells(i, 1).Value = ActiveWorkbook.Worksheets(shtSheet1).Cells(j, 1).Value Then
            For c = 2 To 22
                If Not ActiveWorkbook.Worksheets(shtSheet2).Cells(i, c).Value = ActiveWorkbook.Worksheets(shtSheet1).Cells(j, c).Value Then
                    ActiveWorkbook.Worksheets(shtSheet2).Cells(i, c).Interior.Color = vbYellow
                    mydiffs = mydiffs + 1
                End If
            Next
        Exit For
        End If
        If j = cnt1 Then
            ActiveWorkbook.Worksheets(shtSheet2).Cells(i, 1).Interior.Color = vbRed
        End If
    Next
Next
'Display a message box to demonstrate the differences and if there is a new entry on the second sheet
'MsgBox mydiffs & ":differences found, " & noexist & ":no exist", vbInformation
ActiveWorkbook.Sheets(shtSheet2).Select
End Sub

 

[Fluff]

You're welcome & thanks for the feedback