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.doc File Extension

Learn what a .doc file is, which apps open legacy Word documents, how Poly supports them, and when to convert one to DOCX or PDF.

File extension details for .doc

Full Support
File typeMicrosoft Word 97-2003 document
MIME type
application/msword
EncodingBinary, commonly an OLE Compound File Binary document
Operating systemsWindows, macOS, Linux
Opens withMicrosoft Word, LibreOffice Writer, Word for the web
Poly supportYes. Poly provides rich document support for DOC files.
Indexed by PolyYes. Poly indexes supported text, OCR results, and page-level similarity.
Preview in PolyYes. DOC files open in a connected Office viewer.
Poly agentYes. The Poly agent can read successfully processed pages.

What kind of file is a .doc?

A .doc file is usually a legacy Microsoft Word document. Word 97 through Word 2003 used this binary format by default, and its registered MIME type is application/msword. Current versions of Word still support it for compatibility.1

Most Word 97-2003 documents are OLE Compound File Binary containers. They often begin with the eight bytes D0 CF 11 E0 A1 B1 1A E1, but that signature is not unique to DOC. Old Excel, PowerPoint, and other compound files can share it. A reliable check also looks for Word-specific streams such as WordDocument and 0Table or 1Table.2

Very old Word files also use .doc but may have different internal structures. Renaming a file to .doc does not turn it into a Word document.

How do I open a .doc on my computer?

  • On Windows or macOS, open it with Microsoft Word.
  • On Linux, LibreOffice Writer is a common choice. LibreOffice provides filters for several Word binary generations.3
  • In a web browser, upload it to Word for the web. Viewing is supported, but browser editing creates a modern copy rather than saving back to the old binary format.4

Browsers do not render DOC files by themselves. Be cautious with unexpected attachments because a DOC can contain VBA macros, embedded objects, and external links. Keep active content disabled unless you trust the sender and understand what it does.5

Poly support for .doc

Poly recognizes .doc filenames and gives supported documents a first-page thumbnail, a connected Office preview, full-text search, OCR when needed, page-level similarity, and agent reading. This makes the document findable by its words as well as by visually similar pages.

The preview requires an internet connection. Password-protected, damaged, or unusually old documents may not process successfully. Poly does not run macros or external data connections.

History of .doc

The suffix predates the Word 97-2003 format that most people now call DOC. The original application/msword registration was submitted in July 1993 and covered multiple Word generations, including Word 4 and 5 for Macintosh, Word for Windows 2.0, and Word 6.6

Word 97 later established the binary generation documented in Microsoft's [MS-DOC] specification. That format remained Word's default through Word 2003. Word 2007 switched the default to the Office Open XML .docx format, while retaining the ability to open and save .doc files.12

Working with .doc and alternatives

Choose a destination based on what the recipient needs:

FormatBest useMain tradeoff
.docPreserving an original or supporting a legacy workflowOlder binary format with active-content and compatibility concerns
.docxContinued editing in current office softwareConversion can shift fonts, fields, or layout
PDFSharing a stable review or print copyHarder to edit as a structured document
Plain textRecovering just the readable wordsLoses layout, images, comments, and formatting

Keep the original, convert with Word or LibreOffice, and compare the result. Pay special attention to page breaks, fonts, tables, tracked changes, equations, and embedded objects. Changing report.doc to report.docx only changes the name; a word processor must read the binary file and write a new DOCX package.

Footnotes

  1. Microsoft. File Format Reference for Word, Excel, and PowerPoint. Microsoft identifies .doc as the Word 97-2003 binary document format and .docx as the modern XML-based default. ↩ ↩2
  2. Microsoft. MS-DOC: Word (.doc) Binary File Format. The specification covers Word 97, 2000, 2002, and 2003 documents. ↩ ↩2
  3. The Document Foundation. File Conversion Filter Names. LibreOffice documents its Microsoft Word binary import and export filters. ↩
  4. Microsoft. Differences Between Using a Document in the Browser and in Word. Word for the web converts legacy documents before browser editing. ↩
  5. Microsoft. Protect Yourself From Macro Viruses. Microsoft recommends enabling active content only when its source is trusted. ↩
  6. Internet Assigned Numbers Authority. application/msword Media Type Registration. The registration is dated July 22, 1993 and describes several early Word versions. ↩
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