What is the WKS file format?
.wks is a spreadsheet document format associated with Microsoft Works. Spreadsheet files store data in cells organized in rows and columns. Microsoft Works was not a simplified version of Excel but a standalone integrated suite - bundling word processing, spreadsheets, and a database module - aimed at home users as a more affordable alternative to the Office package.
The .wks extension is also shared with the Lotus 1-2-3 worksheet format; both use a binary record-based structure, but they are distinct formats. Works spreadsheet files are flat little-endian streams of type-length-value records with no compression or encryption.
Microsoft Works was first released in 1987; the .wks extension was used through the Works 4.x line, after which new versions switched to the .xlr format. Works was discontinued in 2009, when the free Office 2010 Starter edition displaced it.
Microsoft Excel supported .wks import up to version 2003; later Excel versions dropped the Works importer entirely. Today, LibreOffice Calc (via its libwps filter) is the most reliable tool for opening legacy .wks files. For long-term preservation, converting to .xlsx or ODS is recommended.
Security & safety
RISK: LOWA WKS file is plain spreadsheet data without the macro/scripting payload found in modern Office files, so opening one is low risk. The real concern is data preservation: WKS is obsolete and modern Excel can't read it, so convert important data to XLSX/ODS while LibreOffice still ships the libwps Works importer. Avoid sketchy "WKS converter" download sites (potential adware); use the official LibreOffice or Gnumeric.
Format details
in a nutshell- Lotus 1-2-3 Worksheet (WKS) - The original .wks was Lotus 1-2-3's first-generation worksheet format (1983); Works borrowed its record layout. LibreOffice/Gnumeric open both.
Programs that open WKS files
Windows3 apps
Microsoft Works
Paid The original program if you still have it installed - discontinued in 2009, so only for legacy machines. Use LibreOffice on modern systems. 
Gnumeric
Open-source Open the .wks - Gnumeric reads the Works/Lotus WKS family. Useful for tricky legacy files. 
LibreOffice Calc
Open-source File > Open the .wks; Calc imports Microsoft Works spreadsheets via libwps. Then Save As to XLSX/ODS/CSV. The most reliable free opener. 
macOS1 app
Linux2 apps
LibreOffice Calc
Open-source Open the .wks and convert; bundled with most Linux desktops, includes the libwps Works importer. Technical details
deep spec| Format type | Proprietary binary spreadsheet |
| Byte order | Little-endian |
| MIME type | application/vnd.ms-works |
| File structure | Flat stream of type-length-value (TLV) records from a BOF (Beginning-of-File) record to an EOF record |
| File signature | Binary header only; no ASCII magic string - identified by the version word in the leading BOF record |
| Grid limit | 256 columns × 16,384 rows |
| Encryption | None - no native password protection |
| Worksheets per file | Single worksheet only (no multi-sheet support) |
| Formula storage | Formulas stored with cached result values alongside the formula expression |
| Extension conflict | Shared with Lotus 1-2-3 (.wk1 family); the .wks extension identifies two distinct binary formats |
| Superseded by | .xlr (Works 2000 and later), then .xlsx / .ods for modern workflows |
| Associated platforms | Windows, MS-DOS (Works 1.x-2.x), classic Mac OS |
| Best modern opener | LibreOffice Calc via libwps import filter; also Gnumeric |
| Released | 1987 (Microsoft Works 1.0); .wks spreadsheet through the Works 4.x/2000 line |
| Latest version | Microsoft Works 9.0 (2007); Works discontinued 2009. Later Works used .xlr for spreadsheets |
| Specification | fileformats.archiveteam.org |
WKS conversions
Community Q&A
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