SDW (StarOffice Writer Document)
The native word processor format from the office suite that predated OpenOffice and sparked a generation of open-source alternatives.
| Full name | StarOffice Writer Document |
| Extension | .sdw |
| MIME type | application/vnd.stardivision.writer |
| Developer | Star Division (later Sun Microsystems) |
| Released | c. 1990s (used through StarOffice 5.x) |
| Type | Word processing document |
| Container | Microsoft Compound File (OLE2) |
| Succeeded by | SXW (StarOffice 6, 2002) |
What is a SDW file?
SDW is the native document format of StarWriter, the word processor bundled with StarOffice. Star Division, a German software company founded in 1985 by Marco Börries, created and maintained the format through StarOffice version 5.x. When Sun Microsystems acquired Star Division in 1999 and open-sourced the code in 2000, SDW files became a relic of that proprietary era.
An SDW file stores a formatted word processing document produced by StarOffice Writer. It holds text, fonts, paragraph styles, embedded images, and basic page layout settings in a single binary file. Internally the format uses Microsoft's OLE2 Compound File structure, the same container technology that underlies older .DOC files, making it a structured filesystem packed inside one file. The format was replaced by SXW in StarOffice 6 (2002), which used an XML-based layout closer to what became the OpenDocument standard.
History
Star Division was founded in Lüneburg, Germany in 1985 by Marco Börries, who had written the first StarWriter at age 16 for the Zilog Z80 microprocessor. The suite grew through the late 1980s and 1990s across MS-DOS, OS/2, and Windows, accumulating an estimated 25% market share in Germany and over 25 million sales worldwide. Sun Microsystems bought Star Division on August 5, 1999 for roughly $59.5 million, open-sourced the code in July 2000, and SDW was phased out when the XML-based SXW format arrived with StarOffice 6 in 2002.
How it works
SDW files wrap their content in the OLE2 Compound File Binary Format, a container that works like a mini filesystem with named streams and storages. The main text stream holds formatted paragraphs encoded in Star Division's proprietary binary scheme. Separate streams store styles, embedded objects, document metadata, and drawing layer data. Because the format is closed and undocumented in detail, tools that support it rely on reverse-engineered specifications.
What it is used for
- Recovering old documents created in StarOffice 3, 4, or 5 from the 1990s
- Archiving and digitizing legacy office files from institutions that ran StarOffice on Linux or Windows
- Converting SDW files to modern formats like DOCX or ODT for continued editing
- Digital preservation projects that catalog pre-OpenDocument word processing formats
How to open it
LibreOffice Writer can open SDW files directly since it inherits the StarOffice codebase, making it the most reliable choice. Apache OpenOffice and the older OpenOffice.org also support the format, and online converters can turn SDW into DOCX or PDF without installing software.
Pros and cons
Strengths
- Preserves formatting from StarOffice documents that predate OpenDocument
- Supported natively by LibreOffice, the most widely used free office suite
- OLE2 container keeps all document parts in a single portable file
- Readable by several open-source tools due to reverse-engineering work
Trade-offs
- Proprietary and undocumented binary format with no official public specification
- Superseded over 20 years ago and no longer produced by any current application
- Conversion to modern formats can lose complex formatting or embedded objects
- Very limited software support outside LibreOffice and its direct derivatives
Convert SDW files
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SDW FAQ
Can I open an SDW file without StarOffice?
Yes. LibreOffice Writer handles SDW files on Windows, macOS, and Linux at no cost. It inherited SDW support from the original StarOffice source code that Sun open-sourced in 2000.
What replaced the SDW format?
StarOffice 6 (released in 2002) replaced SDW with SXW, an XML-based format. SXW in turn gave way to the ODF ODT format, which is now the standard for open word processing documents.
Is SDW the same as the file format used by AmiDraw?
No. There is an unrelated format also called SDW used by AmiDraw on the Amiga platform. The StarOffice Writer SDW and the AmiDraw SDW share only the extension and nothing else.
Why does the SDW file use an OLE2 container?
Star Division adopted the Microsoft Compound File (OLE2) structure during the 1990s when it was a common cross-platform container for office documents, similar to how older versions of Microsoft Word used .DOC files built on the same container.