How to Open and Convert Lotus 1-2-3 Files on Windows 11

TL;DR

On Windows 11, Lotus 1-2-3 files (.123, .wk1, .wk3, .wk4, .wks, .wb1, .wb2, .wb3) do not open natively in Microsoft Excel. You can try LibreOffice Calc for light viewing, use IBM Lotus 1-2-3 if you still license it, or convert locally to XLSX, CSV, or PDF with a dedicated tool like Lotus Converter so Excel and your archive workflows behave the way you expect.

Why Excel may say no on Windows 11

Lotus 1-2-3 worksheets use proprietary binary formats that changed several times between WK1, WK3, WK4, and SmartSuite .123. Microsoft removed Lotus 1-2-3 import filters from Excel years ago, so even the latest Microsoft 365 build cannot reliably open most of these files. Windows 11 still shows the icons and filenames in File Explorer, but no built-in spreadsheet engine knows how to read them.

If a double-click produces an "unknown app" prompt or Excel opens an empty grid, that is normal for many legacy Lotus files—not a sign that the file is corrupted.

What you actually need

In practice, your goal is usually one of two things: quickly see the data, or produce a modern, editable file you can review, archive, or import into reporting and AI workflows. Each option below targets one of those goals.

Three options for opening Lotus 1-2-3 files in 2026

1. LibreOffice Calc (free, basic support)

LibreOffice Calc can open some .wk1, .wk3, and .wk4 files for viewing. Results vary with workbook complexity—macros, named ranges, and protected sheets are where fidelity often breaks. If you only need a quick look at a small workbook, it is worth trying first.

2. IBM Lotus 1-2-3 / SmartSuite (when fidelity matters)

If layout and formula fidelity must match the original exactly, the authoritative app is still Lotus 1-2-3. That path is not wrong, but it is rare on modern Windows 11 hardware and IBM no longer sells SmartSuite. Most teams prefer to convert once to XLSX or PDF and retire the binaries after validation.

3. Lotus Converter (convert to XLSX, PDF, CSV, and more)

Lotus 1-2-3 Converter is built for the "no Lotus 1-2-3 installed" scenario on Windows. Select files or whole folders, choose XLSX, PDF, CSV, HTML, Markdown, or XLS, and convert entirely on your PC—no cloud upload, no internet round-trip, no third-party server.

A workflow that scales for archives

Start with a small sample set from each extension family (.wk1, .wk3, .wk4, .wks, .123) and convert them into a separate output folder. Open the resulting XLSX in Excel, sample formulas and totals, and only then run the full archive in batch mode.

For archives that include payroll, pricing, customer lists, or operating forecasts, local conversion keeps the data on the workstation and out of online services—which is increasingly the default expectation for IT and security teams.

A quick note on "free online" Lotus converters

Uploading legacy spreadsheets to a random web converter sends business data to someone else's infrastructure. For personal drafts that may be fine; for regulated, financial, or competitive data it is a non-starter. When in doubt, keep processing local—especially on Windows 11 machines that already meet your security baseline.

Bottom line

You do not need a working Lotus install on Windows 11 to recover the data inside legacy .wk1, .wk3, .wk4, and .123 files. Pick the tool that fits your fidelity and privacy requirements, sample the output, and modernize the archive once.