DOC file format
DOC is the binary Word format used before Office 2007. Everything still opens it, but it is larger, less portable and carries the macro baggage of a different era.
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What is DOC?
DOC dates back to Word for MS-DOS in 1983 and spent two decades as the de facto standard for digital documents. Internally it is an OLE compound file — a small filesystem inside a file, storing text, formatting and editing history as binary streams. Microsoft kept the specification private for most of its life, so other software had to reverse-engineer it.
That is why old DOC files sometimes open imperfectly today: tables shift, fields break, embedded objects vanish. The format also stored more than authors expected. Deleted text could survive in the file, and fast-save fragments occasionally exposed material the writer believed was gone — a genuine source of document leaks in the 2000s.
DOC also belongs to the era when macro viruses spread through documents, which is why modern Office opens .doc files in Protected View and blocks macros from the internet by default. Unless a specific old system requires DOC, converting an archive to DOCX makes it smaller, safer and more portable.
| Extension | .doc |
|---|---|
| Category | Document |
| MIME type | application/msword |
| Released | 1983 |
| Developed by | Microsoft |
| Compression | None (uncompressed) |
DOC: frequently asked questions
- Should I still save documents as DOC?
- No, unless a specific recipient or legacy system demands it. DOCX is smaller, more robust, readable by more software and better supported by everything current. DOC survives only as a compatibility format for workflows that were never updated.
- Why does my old DOC file not open properly?
- Because the binary format was undocumented for years and applications had to guess at parts of it. Complex tables, fields, embedded objects and older Word features are the usual casualties. Converting to DOCX generally normalises the content and stabilises what still reads.
- Are DOC files less safe than DOCX?
- They carry more historical risk. Macro viruses spread through DOC files in the 1990s and 2000s, so modern Office opens them in Protected View. DOCX separates macros into the distinct .docm extension, making it obvious when a document can execute code.
- Where do DOC files still come from?
- Government forms, legal templates, university document banks and internal systems built in the 2000s that nobody has revisited. They also appear when someone uses an old copy of Word or an application that only knows how to export the legacy format.
- Will converting DOC to DOCX change my layout?
- Usually not visibly. Plain text, headings, lists and simple tables carry over faithfully. Very old documents with complex frames, WordArt or legacy fields can shift slightly, so it is worth a quick look at the first and last pages after converting.
- How much smaller is DOCX than DOC?
- Typically 50-75% smaller for the same content, because DOCX compresses its XML while DOC stores binary data uncompressed along with revision remnants. The saving is largest on long documents and those that have been edited many times.