What is XLSX? XLSX, short name for Excel Spreadsheet XML, is used as the file extension for spreadsheet files in Excel Spreadsheet XML format. .XLSX files are binary files that can be opened by Microsoft Excel software. See the sample .XLSX file included below.

File Extension: .XLSX

MIME Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

File Content: Spreadsheet

.XLSX files are spreadsheet files saved in Excel Spreadsheet XML format. Here are the first 64 bytes of a sample .XLSX file dumped in HEX values:

50 4b 03 04 14 00 06 00 08 00 00 00 21 00 7c 6c PK.............l
98 16 6c 01 00 00 a0 05 00 00 13 00 08 02 5b 43 ..l............C
6f 6e 74 65 6e 74 5f 54 79 70 65 73 5d 2e 78 6d ontent_Types..xm
6c 20 a2 04 02 28 a0 00 02 00 00 00 00 00 00 00 l...............

.XLSX files are actually ZIP files. See the ZIP identifier "PK" in the above HEX dump. When an .XLSX file is extracted by a ZIP tool, you will these files and folers:

<DIR>          docProps
<DIR>          xl
         1,440 [Content_Types].xml
<DIR>          _rels

.XLSX Excel Spreadsheet XML file sample: Click sample.xlsx to download.

.XLSX Excel Spreadsheet XML files can be created and modified by these software:

• Apache OpenOffice - Opens and creates .XLSX Excel Spreadsheet XML files
• Microsoft Excel 2010 - Opens and creates .DIF Data Interchange Format files