What is DOC?
Complete guide to the DOC file format
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What is DOC?
DOC is the binary file format used by Microsoft Word from version 1.0 in 1983 through Word 2003. It stores word processing documents including text, formatting, images, tables, embedded objects, and revision history in a proprietary binary structure. DOC files use Microsoft's Compound Document File Format (also called OLE Structured Storage), which was designed for Windows and is closely tied to the Windows COM/OLE infrastructure.
In 2007 Microsoft replaced DOC as the default format with DOCX, which uses the open XML-based Office Open XML standard. Despite being superseded, DOC files remain in use because they are still fully supported by all versions of Microsoft Word, LibreOffice, and Google Docs. Organizations with documents created before 2007 often retain DOC files rather than converting them. DOC files can also contain macros, which has made the format a common vector for malware distribution.
How the DOC Format Is Structured
A DOC file is stored inside Microsoft's Compound File Binary format, an internal mini-filesystem of named streams and storages built on OLE Structured Storage.[3] The main document text lives in a WordDocument stream, while formatting, style, and structural data are kept in separate streams referenced by a file information block.[3] This layout, tied closely to Windows COM/OLE, makes the format complex to parse correctly without the official specification.[1]
History and the Shift to DOCX
The binary DOC format evolved across many Word versions and was the de facto standard for word processing for two decades before Word 2007 made the XML-based Office Open XML format (DOCX) the default.[2] Microsoft later published the MS-DOC specification documenting the legacy binary structure for interoperability.[3]
Security Considerations
Because DOC files can embed VBA macros, the format has been a recurring vehicle for malware, with malicious documents using macros to execute code when opened.[4] The Library of Congress notes the format's proprietary, undocumented history as a factor weighing against its suitability for long-term preservation.[1]
Technical Details
DOC vs Other Document Formats
| Feature | DOC | DOCX | RTF |
|---|---|---|---|
| Structure/type | Binary (OLE)[1] | Zipped XML | Tagged text |
| Editable | Yes | Yes | Yes |
| Layout | Reflowable | Reflowable | Reflowable |
| Spec published by | Microsoft[3] | ECMA / ISO | Microsoft |
| Open/proprietary | Proprietary[2] | Open (vendor-led) | Proprietary spec |
| Best for | Legacy Word docs[4] | Modern Word docs | Simple rich text |
DOC is the legacy binary Word format, since replaced by the XML-based DOCX as the default.
Pros and Cons
Advantages
Supported by virtually all word processors including Word, LibreOffice, WPS Office, and Google Docs.
Necessary for opening and editing documents created before 2007 without format conversion.
Preserves formatting, macros, embedded objects, and revision marks from older Word versions.
Documents created in older Word versions open with their original formatting intact.
Disadvantages
The binary structure is difficult to parse, repair, or read without Microsoft Office or compatible software.
DOC files can contain VBA macros that have historically been used to distribute malware.
Binary DOC files are often larger than equivalent DOCX files which use XML with ZIP compression.
Lacks support for modern Word features added after 2007 and is no longer the format Word saves in by default.
When to Use DOC
Here are the most common situations where DOC is the right choice:
Legacy Document Compatibility
Use DOC when you need to share documents with organizations or software that require Word 97-2003 compatibility.
Older Client Requirements
Some government and institutional systems still require .doc format for document submissions.
Pre-2007 Archive Access
Open and work with archived DOC documents from pre-2007 word processing systems.
Convert to DOCX
Migrate DOC files to DOCX format using Word or LibreOffice to benefit from the modern XML-based format.
Convert DOC Files
Need to convert your DOC files? Use our free online converter.
Try Document Converter FreeFrequently Asked Questions about DOC
What is the difference between DOC and DOCX?
DOC is the older binary format used before Word 2007. DOCX is the XML-based Office Open XML format introduced in Word 2007. DOCX is smaller, more transparent, and the current default. Word can open and save both formats.
Can LibreOffice open DOC files?
Yes. LibreOffice Writer fully supports DOC files and can open, edit, and save them without conversion.
Are DOC files safe?
DOC files can contain macros that execute code. Only open DOC files from trusted sources and keep macros disabled unless you specifically need them from a trusted document.
How do I convert DOC to PDF?
Use our free converter, Microsoft Word's “Export to PDF” option, or LibreOffice to convert DOC files to PDF.
Can Google Docs open DOC files?
Yes. Google Docs can open, display, and edit DOC files. However, some complex formatting with macros or advanced layout may not be fully preserved.