.WK file extension

To open .WK files on Windows, in Microsoft Excel, use File → Open and select the .wk file (if it fails, try choosing a Lotus 1-2-3-related file type in the file-type dropdown, if available).

To open a .wk file, try Microsoft Excel on Windows; Excel has built-in support for Lotus 1-2-3 formats (notably .wk3) and may import other WK-family spreadsheets. If your Excel version won’t open it directly, use an older Excel install or a converter workflow on a desktop system.

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Last updated: October 13, 2026

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .WK files

Use these platform-specific instructions to open .WK files safely.

Windows

In Microsoft Excel, use File → Open and select the .wk file (if it fails, try choosing a Lotus 1-2-3-related file type in the file-type dropdown, if available).
If Excel won’t open it, try an older Excel version known to handle Lotus imports (Excel 2003-era support is documented for Lotus formats like .wk3), then Save As a modern format (e.g., .xlsx or .csv).
If you suspect the file is really a specific WK variant (e.g., .wk3/.wk4), try renaming the extension to the most likely variant and open again (only after making a copy).

Full Windows guide

Mac

If you have Microsoft Excel for Mac, try File → Open; if it does not import the file, move the file to a Windows PC with Excel and convert it there.
As a fallback, ask the sender for a re-saved copy in .xlsx or .csv from a desktop spreadsheet program that can import Lotus 1-2-3 WK-family files.

Full Mac guide

Linux

Try opening the file using a desktop spreadsheet program that can attempt Lotus import; if import fails, transfer the file to a Windows machine with Microsoft Excel and convert it.
After conversion on another machine, bring the exported .xlsx or .csv back to Linux for regular use.

Full Linux guide

iOS

On iPhone/iPad, don’t expect reliable direct opening; transfer the .wk file to a desktop (preferably Windows with Excel) to convert it to .xlsx or .csv, then open the converted file on iOS.

Full iOS guide

Android

On Android, direct support is uncommon; convert the .wk file on a desktop (preferably Windows with Excel) to .xlsx or .csv, then open the converted file on Android.

Full Android guide

Security notes

WK-family Lotus spreadsheets are legacy binary files; treat them as untrusted input because old/complex parsers can have vulnerabilities, especially in very old office software.
Prefer opening unknown .wk files in a modern, fully patched application and convert/export to a safer modern format for ongoing use.
Be cautious with attachments labeled .wk that don’t behave like spreadsheets (unexpected size, prompts, or opening in unrelated apps); the extension can be misleading or intentionally spoofed.

Can't open this file?

These are the most common causes and fixes when .WK files fail to open.

Common reasons

Excel says the file format is not valid or won’t open
Garbage characters or missing formatting after import
File extension is “.wk” but software expects .wk1/.wk3/.wk4/.wks

Fix steps

Make a copy of the file, then try opening it in a different Excel version (older versions may have broader Lotus import support).
If you can determine the variant, try renaming the copy to .wk1, .wk3, or .wk4 and attempt open again.
If it opens, immediately Save As .xlsx or export .csv to preserve access.

Recover a deleted or lost .WK file

If the file was deleted by mistake or the drive was formatted, data recovery software may be able to get it back. Stop writing to that drive right away, because new data can overwrite what you want to recover.

MiniTool Power Data Recovery

Windows software that recovers deleted or lost files from PCs and external drives such as HDDs, SSDs, USB drives and memory cards, after deletion, formatting or a crash.

Wondershare Recoverit

Windows and Mac software that recovers deleted or lost files from computers and external drives such as HDDs, SSDs, USB drives and SD cards.

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OS-specific troubleshooting

What is a .WK file?

“.wk” is commonly used as a shorthand for Lotus 1-2-3/Symphony spreadsheet files in the WK family (extensions like .wk1, .wk3, .wk4 are explicitly documented as Lotus 1-2-3 spreadsheets). These are legacy binary spreadsheet formats used by older DOS/Windows office suites. Compatibility varies by application and version; modern tools may need import/conversion rather than native editing.

Background

Lotus 1-2-3 was a widely used spreadsheet program, and its file formats used several related extensions, including wk1, wk2, wk3, wk4, and wks. In practice, users may encounter files labeled “.wk” as part of this legacy family, especially when extensions were shortened, renamed, or lost during transfers.

Modern use is mostly about recovery and migration: opening an old spreadsheet to extract values, print, or convert to a newer format. Microsoft Excel has historically supported opening Lotus 1-2-3 files (documentation for Excel 2003 discusses Lotus imports such as .wk3), though support can depend on the exact variant and the Excel version.

Other tooling acknowledges the WK family as Lotus/Symphony-readable: SPSS documentation describes “WK” as a type that can read “any Lotus 1-2-3 or Symphony file.” This reinforces that “WK” is treated as a family label rather than one single contemporary standard.

Because these are older binary formats, interoperability can be imperfect (format features, macros, charts, and cell formatting may not convert exactly). The safest practical approach is often: open once in a compatible desktop app, then save/export to a modern format for long-term use.

Known aliases: .wk1, .wk2, .wk3, .wk4, .wks, .123

Common .WK issues

Excel says the file format is not valid or won’t open

“.wk” is a family label and may not match the exact Lotus 1-2-3 variant; some Excel versions import only certain variants (Excel documentation explicitly discusses Lotus files like .wk3).

Make a copy of the file, then try opening it in a different Excel version (older versions may have broader Lotus import support).
If you can determine the variant, try renaming the copy to .wk1, .wk3, or .wk4 and attempt open again.
If it opens, immediately Save As .xlsx or export .csv to preserve access.

Garbage characters or missing formatting after import

Legacy Lotus/Symphony spreadsheets are binary and feature mapping to modern spreadsheets may be incomplete, especially for formatting, charts, or nonstandard encodings.

After opening, compare totals and key cells against expected values; focus on recovering the data first.
Try saving to .csv for clean data transfer (values only), then re-apply formatting in a modern spreadsheet.

File extension is “.wk” but software expects .wk1/.wk3/.wk4/.wks

Some tools and documentation refer to Lotus spreadsheets using more specific extensions (wk1/wk3/wk4/wks). A file may be mislabeled or renamed during email/backup transfers.

Ask the sender what program created the file and whether it was Lotus 1-2-3 or Symphony.
Make a backup copy and try renaming the extension to a WK-family extension and re-open in Excel or another importer.

FAQ

Is .wk the same as .wks or .wk1/.wk3/.wk4?

They’re closely related in practice: Lotus 1-2-3 used multiple WK-family extensions (including wks, wk1, wk2, wk3, wk4). “.wk” is often used as a generic label for that family, but the exact variant matters for compatibility.

Can Microsoft Excel open .wk files?

Excel has documented support for opening Lotus 1-2-3 files (for example, Excel 2003 documentation discusses handling Lotus files such as .wk3). Whether your specific .wk opens depends on the actual variant and your Excel version.

What’s the best way to preserve the data long-term?

Open it once in a compatible desktop application (commonly Excel), then save to a modern format such as .xlsx for spreadsheets and/or .csv for values-only export.

Is there an official MIME type for .wk?

No specific MIME type for “.wk” is confirmed by the provided sources; for formal registration, MIME types must appear in the IANA media type registry.

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