What is an FM3 file?
An .FM3 file is primarily a spreadsheet formatting file created by Lotus 1-2-3, a classic spreadsheet program developed by Lotus Software and later acquired by IBM. These files store formatting data—such as fonts, column widths, and cell styles—that apply to the main spreadsheet data file. Alternatively, an .FM3 file can be an FCEUX TAS Editor Movie Capture file. This type of file records gameplay inputs for tool-assisted speedruns in the FCEUX emulator.
How to open FM3 files?
To open a Lotus 1-2-3 .FM3 file, you usually need the original Lotus 1-2-3 software or legacy office suites like IBM Lotus Symphony. Modern spreadsheet tools have largely dropped support for early Lotus formats. If your file is a movie capture, you must open it using the FCEUX emulator on a compatible desktop operating system.
Best practices and troubleshooting
Because the .FM3 extension belongs to completely different applications, identifying the file origin is the first step. Lotus 1-2-3 formatting files are normally found in the same folder as data files with extensions like .WK3. If you open an .FM3 formatting file alone, you will not see the actual spreadsheet text or numbers. Emulation movie captures, on the other hand, require the exact game ROM to function correctly.
Software and tools
You can try opening legacy spreadsheet files with older versions of LibreOffice Calc or Apache OpenOffice, though support for formatting files might be limited. For game recordings, the TAS (Tool-Assisted Speedrun) editor inside FCEUX is the only software that can read the specific movie data.
Summary
Since .FM3 has multiple possible meanings, we recommend using viewer.online/fm3 to identify the actual format of your file. viewer.online/fm3 can analyze .FM3 files to identify the exact format and creator software, inspect the file structure, extract readable text, and check whether an online preview is available. Ultimately, viewer.online/fm3 is useful for identifying, inspecting, and understanding .FM3 files without installing old software or dealing with compatibility problems.