Microsoft Word DOC MIME Type

What does application/msword mean?

application/msword is the registered media type for binary Microsoft Word documents. It is most closely associated with .doc files. Word 97 through Word 2003 used the documented Word Binary File Format as their default document format, and current Word releases can still open and save it for compatibility.¹²

The type is older and broader than that one format generation. Its July 1993 IANA registration named Word 4 and 5 for Macintosh, Word for Windows 2.0, and the then-forthcoming Word 6 format. It even defined an optional version parameter, although that parameter is rarely seen now.¹

That history means a .doc suffix does not identify one byte-level format by itself. Very old Word files and Word 97-2003 files can share the extension while using different internal structures. Modern format identification should inspect both the file and its context instead of trusting the suffix alone.³

The .dot extension identifies a legacy Word template. Microsoft and LibreOffice both associate Word 97-2003 templates with the same binary Word family, and LibreOffice maps .dot to application/msword.²⁴

Why is 1993 listed as the registration date?

Paul Lindner submitted the application/msword registration on July 22, 1993, with Microsoft listed as the company contact.¹ Word documents existed before then, but 1993 is when this MIME label entered the registry.

The binary format continued to evolve. Word 6.0, released in 1993, moved Word documents into Microsoft's OLE Compound File Binary container. Word 97 changed the detailed document structures inside that container. The current Microsoft [MS-DOC] specification describes the Word 97-2003 generation used by Word 97, Word 2000, Word 2002, and Word 2003.³⁵

DOC remained available after Word 2007, but DOCX became the default. Microsoft describes the Word binary format as superseded by ECMA-376, the Office Open XML standard behind modern Word documents.⁶⁷

How can you identify a DOC file?

Most Word 97-2003 DOC files begin with this eight-byte Compound File Binary signature:

D0 CF 11 E0 A1 B1 1A E1

That signature is useful but not unique to Word. Older Excel files, PowerPoint files, MSI installers, and other OLE compound documents can begin with exactly the same bytes. A Word 97-2003 file also contains a WordDocument stream, a 0Table or 1Table stream, and a File Information Block that ties the document's text and objects together.³⁸

For that reason, this page does not present the CFB header as a definitive magic number for application/msword. A reliable detector checks the compound-file directory and Word-specific records. A .doc filename plus the shared CFB signature is only a strong hint.

Older Word files complicate detection further because not every document covered by the historical MIME registration uses the Word 97 compound structure. If a trusted word processor opens an old .doc but a modern format-identification tool does not recognize it as [MS-DOC], the file may belong to an earlier Word generation rather than being corrupt.

How do you open an application/msword file?

General-purpose browsers do not natively render DOC files. Use an office application or an online document service:

• Microsoft Word supports Word 97-2003 .doc documents and .dot templates.²
• LibreOffice Writer has import and export filters for several Word binary generations, including Word 97-2003 documents and templates.⁴
• Word for the web can display .doc and .dot files. To edit one in the browser, it saves a new DOCX or DOTX copy and cannot save back to the old binary format.⁹

Support in Poly

Poly recognizes the exact application/msword identifier and infers it from a .doc filename. It categorizes the file as a document, converts it to PDF, and sends the converted pages through the same processing path as a PDF.

After conversion, Poly:

• Generates a thumbnail set from the first rendered page.
• Records the page count and stores a PDF representation.
• Extracts page text, with OCR fallback where needed.
• Creates page-level visual embeddings for similarity search.
• Lets the agent read the converted document as page text and rendered page images.

Document processing has two code-enforced limits: the source must be no larger than 1 GiB, and page rendering, OCR, and page-level embeddings cover at most 1,024 pages. Password-protected, malformed, or unsupported legacy documents can fail conversion. When conversion fails, Poly cannot produce the page-aware index or agent-readable representation described above.

The in-app preview follows a different path. Poly opens Word documents in Microsoft's hosted Office viewer using a temporary URL, so the preview requires an internet connection. It is not an offline rendering of Poly's converted PDF.

Poly does not currently infer .dot as application/msword from the filename. A correctly labeled application/msword template can enter the document path, but a filename-only .dot upload does not receive the same specific type mapping.

Should you convert DOC to DOCX or PDF?

Choose the destination based on whether the result needs to remain editable:

LibreOffice can convert a document without opening its graphical interface:

soffice --headless --convert-to pdf --outdir converted input.doc

Microsoft recommends saving a DOC document as DOCX, or as DOCM when macros must be retained. It also recommends keeping a backup and checking the result for content or layout changes.¹⁰

Renaming report.doc to report.docx does not perform a conversion. A converter must parse the binary records and write a new package.

Security and privacy considerations

Legacy Word documents can carry VBA macros, embedded OLE objects, external links, and encrypted content. Microsoft warns that active content can contain viruses or other hazards and advises against enabling it unless you understand and trust it.¹¹ Opening an unexpected attachment in Protected View or an isolated, maintained environment is safer than enabling content immediately.

The original 1993 MIME registration said that no security considerations were known.¹ That historical statement does not reflect what is now understood about complex Office documents. Treat application/msword as active-capable input, not as harmless text.

DOC files may also preserve properties such as author, title, company, comments, creation times, and custom metadata. Tracked changes, comments, hidden text, and embedded objects can reveal material that is not obvious in the final page view.³ Inspect both document properties and revision content before publishing a sensitive file.

Conversion is not sanitization. A PDF copy may be more convenient to review and share, but keep the source quarantined if its origin is uncertain, and do not assume a successful preview proves that the original document is safe.

DOC compared with DOCX

DOCX is usually the better editable interchange format for a new document. Keep DOC when a legacy workflow requires it or when preserving an original file is important. Keep a PDF alongside either format when a stable review copy matters.