.XLSX

Office Open XML Workbook

Introduction

XLSX is the default format of Microsoft Excel since Excel 2007, replacing the older binary .xls. Like DOCX it belongs to Office Open XML (ECMA-376 and ISO/IEC 29500): a ZIP archive of XML files holding the workbook, one part per worksheet, the text shared between cells, the styles, and any charts, pictures and pivot tables.

.xlsm is the same layout with macros, and .xltx a template.

Software

Structure

xl/workbook.xml lists the sheets, and each sheet lives in its own part such as xl/worksheets/sheet1.xml. A sheet holds rows of cells (c), each with its reference, like A1, a value (v) and optionally a formula (f). Text is usually not stored in the cell: the cell holds a number that indexes xl/sharedStrings.xml, so repeated text is stored once. Number formats, fonts and fills live in xl/styles.xml.

  1. zip[Content_Types].xml, _rels/.relsXML
  2. zipxl/workbook.xml the sheets and defined namesXML
  3. zipxl/worksheets/sheet1.xml … one part per sheetXML
  4. zipxl/sharedStrings.xml the text used in cellsXML
  5. zipxl/styles.xml number formats, fonts, fills, bordersXML
  6. zipdocProps/ title, author and datesXML
The main parts inside an XLSX package.