The File Extensions Database

.12M File Extension

  • Developer by: IBM
  • Category: Spreadsheet Files

What is an .12M file?

.12M is Lotus 1-2-3 SmartMaster File

A 12M file is a spreadsheet created by Lotus 1-2-3, which is part of IBM Lotus SmartSuite. It contains a pre-designed spreadsheet that allows a user to enter information to create forecasts, financial statements, and budgets. 12M files also include formulas, formatting, and print ranges.

Lotus 1-2-3 was first developed by Lotus Development Corporation, which was bought by IBM in 1995. The "1-2-3" refers to the program's three main capabilities: 1) spreadsheet functions, 2) creating charts and graphs, and 3) basic database operations.

NOTE: Lotus 1-2-3 was popular in the 1980s and early-90s. However, it was overtaken by Microsoft Excel in the 90s and was officially discontinued in 2013.

Programs that open Lotus 1-2-3 SmartMaster File
IBM Collaboration Solutions

How to solve problems with 12M files

  • Associate the 12M file extension with the correct application. On :
    Windows: Right click on any 12M file and then click "Open with" > "Choose another app". Now select another program and check the box "Always use this app to open *.12M files". Mac: Right click (or Ctrl-click) the 12M file, then click "Open with" > "Other...". Then choose another program and check the "Always Open With" box. Linux: Right click on the file, and select "Open with" and choose another program. iPhone: Tap the file. If you do not see an app to open the file, then tap Share "Share" and choose an app. Alternatively, save the file. Then open the Files app Files app. There long-press on the file, then release your finger. You will see a black menu bar. Then tap "Share" and select an app. Android: Tap the Settings icon on your smartphone, then tap on the Apps section. There tap the Options icon in the top right-hand corner of the screen to change the default apps.
  • Update your software that should actually open .12M is Lotus 1-2-3 SmartMaster File. Because only the current version supports the latest 12M file format. Search, therefore, e.g. on the IBM manufacturer website after an available .12M is Lotus 1-2-3 SmartMaster File update.
  • To make sure that your 12M file is not corrupted or virus-infected, get the file again and scan it with antivirus software.