What is the CNV file format?
A .cnv file is a Word converter plugin - a renamed .dll used internally by Microsoft Word to import and export documents in third-party formats. These are not user documents; they are system components installed automatically by Microsoft Office and loaded silently by Word when needed.
Despite the different extension, .cnv files are structurally identical to standard Windows DLLs: each begins with the MZ DOS executable header (4D 5A) at offset 0 and follows the PE (Portable Executable) format. Word loads them automatically when a user opens a supported non-native format - only the converted document is visible to the user.
Well-known examples installed with Word 97-2003 include WPFT632.CNV (WordPerfect 6.x), WPFT532.CNV (WordPerfect 5.x), WORKS632.CNV (Microsoft Works), EXCEL32.CNV (Excel worksheets), and RTFRD32.CNV (RTF reader). These files reside in the Office installation directory, typically C:\Program Files\Microsoft Office\Office\.
With Word 2007 and the Open XML format (.docx), built-in XML-based converters replaced the plugin architecture for mainstream formats, making most .cnv files obsolete.
- Never double-click a
.cnvfile - it is an executable DLL and will not open usefully outside Word. - Files may carry an Authenticode signature from Microsoft.
- They can be inspected with any PE/DLL analysis tool for research or security purposes.
Security & safety
RISK: MEDIUMLegitimate Microsoft CNV files are signed DLLs in the Office installation directory; they are safe. However, malicious actors could name any DLL with a .cnv extension. Never execute or double-click a CNV file received from an unknown source. If found outside the Office installation directory, treat with suspicion.
Format details
in a nutshell- ACD Systems Canvas Drawing File - Canvas (vector illustration/DTP application by ACD Systems) uses .cnv for its native drawing files, containing vector graphics, text, and layout data.
- Lotus Notes Database Conversion File - Some IBM/Lotus Notes installations use .cnv for database conversion data.
Programs that open CNV files
Windows2 apps
Microsoft Word (automatic)
Paid Word loads CNV converters automatically - do not open CNV files manually. If a converter is missing, reinstall Office and select the appropriate converter component.
Any PE/DLL viewer (for inspection only)
Free Use NirSoft DLL Export Viewer or Dependency Walker to inspect exported functions - for developers/sysadmins only. Technical details
deep spec| Binary format | PE (Portable Executable) / Windows DLL |
| Magic bytes | 4D 5A ("MZ") at offset 0 |
| Byte order | Little-endian |
| Container | Windows PE format (identical structure to .dll and .exe) |
| Compression | None (standard PE/DLL structure) |
| Typical file size | 50 KB - 500 KB |
| Code signing | PE checksum in optional header; may carry Microsoft Authenticode signature |
| Associated OS | Windows (Word 6 through Word 2003 era) |
| Storage location | Office installation directory, e.g. C:\Program Files\Microsoft Office\Office\ |
| Function | Implements Word converter API entry points for import/export of specific non-native formats |
| Known examples | WPFT632.CNV, WPFT532.CNV, WORKS632.CNV, EXCEL32.CNV, RTFRD32.CNV |
| MIME type | application/octet-stream |
| Superseded by | Built-in XML converters in Word 2007+ (Open XML / .docx architecture) |
| Released | 1993 (Word 6.0 for Windows; converter architecture established with Word 97) |
| Latest version | Word 97-2003 era; largely unused in Word 2007+ (which uses built-in XML converters) |
CNV conversions
Community Q&A
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