When you print a worksheet or table without gridlines, it can sometimes be difficult to distinguish cell boundaries, as shown in the print preview in this picture:
Printing gridlines is not supported in Excel Online but, you can mimic gridlines by applying borders, like in this picture:
To add a border around each cell, click and drag to select cells that you want included.
On the Home tab, in the Font group, click Borders > All Borders.
The areas with borders will now appear with darker lines.
For a print preview, click File > Print.
Pick the print option you want to preview and click Print.
In the preview, make sure the gridlines look the way you want them to, and then click Print.
If you want to make changes before printing, click the x to close preview and return to the worksheet.
Print gridlines from the Excel desktop application
If you have the Excel desktop application, click Open in Excel, and print gridlines in a worksheet.
For news about the latest Excel Online updates, visit the Microsoft Excel blog.