Background

In ExcelWriter 8, support for the new Open Office XML (OOXML) file formats (XLSX, XLSM) was introduced in ExcelApplication. Since XLSX files have different file format defaults and a different file structure than XLS, ExcelApplication uses a separate code base when working with XLSX files. ExcelWriter's behavior can change between the two file formats in specific situations. These differences are outlined below.

Using the Color Palette

XLS files use a 56 color palette (see Excel's Color Palette Explained). When using ExcelApplication's Workbook.Palette, ExcelWriter will throw an error if Palette.GetColor is called and the color doesn't exist in the palette. Customers are encouraged to use Palette.GetClosestColor to avoid calling for colors that don't exist in the palette. ExcelWriter will approximate which color from the 56 color palette to use.

...

To ensure that output remains consistent while switching to XLSX, we recommend creating a blank XLSX file that has the Normal style set to Arial, size 10. Open that blank template file, rather than creating a template from scratch.

Chart defaults

Some very small minor charting defaults have changed, such as:

...

The workaround is to set these properties explicitly to the desired values in ExcelWriter code. Most ExcelWriter-generated charts will appear the same regardless of whether they are in XLS or XLSX files.

...