138

.138 — Microsoft Excel 1.0 Spreadsheet

Microsoft · 1987

Developer
Microsoft
Category
Spreadsheets
MIME Type
application/vnd.ms-excel
First Released
1987
Open Format
No
File Signature
Not readily documented or consistently recognizable as a distinct signature for this specific .138 variant.
At a Glance
.138
Microsoft Excel 1.0 Spreadsheet

The .138 file extension is an ancient Microsoft Excel spreadsheet format from version 1.0, rarely used today.

Reviewed on April 30, 2026
Compression
Binary
Transparency
N/A
Editability
Low
Best for
Legacy data

Key Features

  • Early graphical spreadsheet data storage
  • Binary file format
  • Proprietary to Microsoft Excel 1.0
  • Limited feature set compared to modern formats

Best For

  • Historical data preservation from Excel 1.0
  • Demonstrating early spreadsheet software capabilities
  • Niche archival purposes

Less Ideal For

  • Modern data analysis and collaboration
  • Sharing data with users of recent Excel versions
  • Complex charts and visualizations
  • Large datasets

Common Use Cases

  • Storing basic financial data
  • Performing simple calculations
  • Creating rudimentary charts
  • Archiving historical spreadsheet data from the late 1980s

How to Open It

  1. Attempt to open with modern Microsoft Excel, which may offer backward compatibility.
  2. Use specialized data recovery or legacy file format converters.
  3. Install an older version of Windows and Microsoft Excel (e.g., Excel 97 or earlier) in a virtual machine.
  4. Convert the file to a more modern format like .xlsx or .csv using a compatible tool.

What is a .138 file?

The .138 file extension represents an early version of Microsoft Excel's proprietary spreadsheet format, specifically for Excel version 1.0. This format was one of the first to bring graphical spreadsheet capabilities to the PC market. While primitive by today's standards, it laid the groundwork for the powerful data analysis and calculation tools we use now. Files in this format are rarely encountered today due to significant advancements and changes in spreadsheet software over the decades. Opening such files typically requires specialized, older software or conversion tools that can interpret this legacy format.

Programs That Open .138 Files

PlatformProgram
WindowsMicrosoft ExcelPaidOfficial
macOSMicrosoft ExcelPaidOfficial

How to Convert .138 Files

FormatMethod
.XLSXMicrosoft Excel, Online Converters
.CSVMicrosoft Excel, Online Converters

Common Problems with .138 Files

⚠️ File cannot be opened by modern software.
Use a converter or attempt opening with a very old version of Excel in a virtual environment.
⚠️ Data corruption or incomplete import.
Try different conversion tools, as compatibility can vary significantly with legacy formats.

Frequently Asked Questions

Is .138 still a relevant file format?▼

No, the .138 format is extremely outdated and rarely used in modern computing. It's primarily of historical interest.

Can I open .138 files with LibreOffice or Google Sheets?▼

Compatibility with these programs is highly unlikely due to the format's age and proprietary nature. Conversion is usually necessary.

Technical Details

This format is a binary file structure developed by Microsoft for its initial release of Excel. It contains worksheet data, formulas, formatting, and potentially charts. Due to its age, the internal structure is vastly different from modern .xlsx files and lacks many features introduced in later versions.

Did You Know?

The .138 extension was specific to the very first graphical version of Microsoft Excel.
This format predates the widely adopted .XLS format by several years.

Security Information

While the .138 format itself is not inherently malicious, opening any legacy file format from unknown sources carries a risk of potential malware or data corruption. Always ensure your antivirus software is up-to-date before attempting to open such files.

Related Extensions

.XLS.XLSX.CSV.XLSM