What is XLSX (Microsoft Excel)?
Complete guide to the XLSX file format
Last updated:
What is XLSX (Microsoft Excel)?
XLSX is the standard file format for Microsoft Excel spreadsheets, introduced in 2007 as part of the Office Open XML standard. It replaced the older binary XLS format.
XLSX files are ZIP archives containing XML files that describe the spreadsheet data, formulas, charts, and formatting. The format is supported by most spreadsheet applications.
How XLSX Works
An XLSX file is an Open Packaging Conventions ZIP container in which a workbook is split across multiple XML parts: each worksheet is its own XML file, while a shared-strings table stores repeated text once to reduce redundancy.[1] Relationships between parts, such as which sheet links to which drawing or chart, are recorded in .rels files, and a content-types part declares the MIME type of every component.[2] This XML-and-ZIP design makes the data inspectable and recoverable compared with the opaque binary XLS that preceded it.[3]
History and Standardization
The format is part of Office Open XML, which Ecma International published as ECMA-376 in 2006 and which ISO/IEC subsequently approved as ISO/IEC 29500.[1] The standard defines two variants, Transitional and Strict, where the transitional form retains legacy compatibility features for migrating older documents.[2] Because it is an open, documented standard, XLSX can be read and written by many applications beyond Excel, including LibreOffice and Google Sheets.[3]
Technical Details
XLSX vs Other Spreadsheet Formats
| Feature | XLSX | CSV | ODS |
|---|---|---|---|
| Structure | XML (zipped)[1] | Plain text | XML (zipped) |
| Formulas | Yes[2] | No | Yes |
| Multiple sheets | Yes[2] | No | Yes |
| Formatting/charts | Yes[2] | No | Yes |
| Standardized by | ECMA/ISO[1] | RFC 4180 | OASIS/ISO |
| Best for | Excel workbooks | Simple data exchange | Open-office sheets |
XLSX stores rich formulas, formatting and multiple sheets, while CSV offers maximum simplicity and ODS provides an open-standard equivalent.
Pros and Cons
Advantages
XLSX is supported by Excel, Google Sheets, LibreOffice, and Numbers.
Full support for complex formulas, functions, and pivot tables.
Built-in charting and data visualization capabilities.
Supports over 1 million rows for large data analysis tasks.
Disadvantages
XLSX is a spreadsheet, not a database - large datasets are better in proper database systems.
Complex XLSX formatting may appear differently in non-Excel applications.
Very large XLSX files can be slow to open and process.
XLSX files with macros can be a security risk when received from unknown sources.
When to Use XLSX (Microsoft Excel)
Here are the most common situations where XLSX (Microsoft Excel) is the right choice:
Financial Analysis
XLSX is the standard for financial modeling, budgeting, and reporting.
Data Analysis
Data analysts use XLSX for data cleaning, analysis, and visualization.
Business Reports
Quarterly and annual reports with charts and pivot tables use XLSX format.
Data Exchange
XLSX is commonly used to exchange structured data between systems.
Convert XLSX (Microsoft Excel) Files
Need to convert your XLSX files? Use our free online converter.
Try Document Converter FreeFrequently Asked Questions about XLSX (Microsoft Excel)
What is the difference between XLS and XLSX?
XLS is the older binary format (before Excel 2007). XLSX is the newer XML-based format that is more compatible and efficient.
Can Google Sheets open XLSX?
Yes, Google Sheets fully supports opening and editing XLSX files.
How do I convert XLSX to CSV?
Use Excel (Save As > CSV) or our free online converter to convert XLSX to CSV for data portability.
Can I open XLSX on Mac?
Yes, Numbers and Microsoft Excel for Mac both fully support XLSX format.
Is XLSX secure?
XLSX files can contain macros. Only open XLSX files from trusted sources as macros can execute malicious code.