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Known Issues and Bugs

This section lists known issues and bugs and gives some information on how to submit bug reports.

Content is Unreadable. Open and Repair

Very occasionally you may encounter a bug which generates an Excel warning when opening an libxlsxwriter file like:

‍Excel could not open file.xlsx because some content is unreadable. Do you want to open and repair this workbook.

This ominous sounding message is Excel's standard warning for any validation error in the XML used for the components of the XLSX file.

If you encounter an issue like this you should open an issue on GitHub with a program to replicate the issue (see below).

Formulas displayed as 'NAME?' until edited

Excel 2010 and 2013 added functions which weren't defined in the original file specification. These functions are referred to as future functions. Examples of these functions are ACOT, CHISQ.DIST.RT , CONFIDENCE.NORM, STDEV.P, STDEV.S and WORKDAY.INTL. The full list is given in the [MS XLSX extensions documentation on future functions] (

When written using write_formula() these functions need to be fully qualified with the _xlfn. prefix as they are shown in the MS XLSX documentation link above. For example:

worksheet_write_formula(worksheet, 0, 0,"=_xlfn.STDEV.S(B1:B10)", NULL);
lxw_error worksheet_write_formula(lxw_worksheet *worksheet, lxw_row_t row, lxw_col_t col, const char *formula, lxw_format *format)
Write a formula to a worksheet cell.

See also Working with Formulas.

Formula results displaying as zero in non-Excel applications

Due to wide range of possible formulas and inter-dependencies between them, xlsxwriter doesn't, and realistically cannot, calculate the result of a formula when it is written to an XLSX file. Instead, it stores the value 0 as the formula result. It then sets a global flag in the XLSX file to say that all formulas and functions should be recalculated when the file is opened.

This is the method recommended in the Excel documentation and in general it works fine with spreadsheet applications. However, applications that don't have a facility to calculate formulas, such as Excel Viewer, or several mobile applications, will only display the 0 results.

If required, it is also possible to specify the calculated result of the formula using the worksheet_write_formula_num() function.

See also Working with Formulas.

Images not displayed correctly in Excel 2001 for Mac and non-Excel applications

Images inserted into worksheets via worksheet_insert_image() may not display correctly in Excel 2011 for Mac and non-Excel applications such as OpenOffice and LibreOffice. Specifically the images may looked stretched or squashed.

This is not an XlsxWriter issue. It also occurs with files created in Excel 2007 and Excel 2010.

Reporting Bugs

Here are some tips on reporting bugs in libxlsxwriter.

Upgrade to the latest version of the library

The bug you are reporting may already be fixed in the latest version of the module.

Check the Changes section to see what has changed in the latest versions.

You can check which version of libxlsxwriter that you are using by compiling and running the following program:

#include <stdio.h>
#include "xlsxwriter.h"
int main() {
printf("Libxlsxwriter version = %s\n", lxw_version());
return 0;
const char * lxw_version(void)
Retrieve the library version.

Read the documentation

Read or search the libxlsxwriter documentation to see if the issue you are encountering is already explained.

Look at the example programs

There are many Example Programs in the distribution. Try to identify an example program that corresponds to your query and adapt it to use as a bug report.

Use the xlsxwriter Issue tracker

The [libxlsxwriter issue tracker] ( is on GitHub.

Tips for submitting a bug report

  1. Describe the problem as clearly and as concisely as possible.
  2. Include a sample program. This is probably the most important step. It is generally easier to describe a problem in code than in written prose.
  3. The sample program should be as small as possible to demonstrate the problem. Don't copy and paste large non-relevant sections of your program.

A sample bug report is shown below. This format helps analyze and respond to the bug report more quickly.

Issue with SOMETHING

I am using libxlsxwriter to do SOMETHING but it appears to do SOMETHING ELSE.

I am using CC version X.Y.Z, OS = uname and libxlsxwriter x.y.z.

Here is some code that demonstrates the problem:

#include "xlsxwriter.h"

int main() {

    lxw_workbook  *workbook  = workbook_new("bug_report.xlsx");
    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);

    worksheet_write_string(worksheet, 0, 0, "Hello", NULL);
    worksheet_write_number(worksheet, 1, 0, 123, NULL);

    return workbook_close(workbook);

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