Working with latest Microsoft Word version, the default file format for saving the document is DOCX. As time moves on, the upcoming generations, working in technology domain, won’t even know how the DOCX format replaced the DOC file format which was the default format for Word 2003 and before. By moving from Doc to Docx, Microsoft fulfilled its promise of open file format standards that was long demanded by companies providing support for word documents.


Those who don’t know the technical details, they may ask if it is really worth considering changing from DOC to DOCX? The answer is none other than Yes! Microsoft had been supporting the DOC extension files since the beginning and new features were being added from time to time. However, the DOC file format’s limitations had large impact on the speed of new features introduction. 

Older Office file formats such as DOC and XLS were stored to disc as binary data and that is why the speed of storing and loading such files was quick. However, the binary file formats had their own limitations due to which it was becoming difficult to manage these with the passage of time. A short comparison of DOC vs DOCX below shows the need of switching from older file format to the new one.

  • DOC file format stores data to disc in binary format that is quicker but results in large file size. DOCX, on the other hand, is based on Office Open XML standards and provides a structured file format that is based on XML and encapsulated in ZIP archive, resulting in small file size.
  • The binary file structure of DOC file format must had to retain interfaces with every new version released in order to avoid crashes. The DOCX file format, based on XML file format, avoids this by having a well structured and organized file format that understands the older formats and supports backward compatibility which was otherwise difficult and tedious with DOC file format.
  • Being binary in nature, managing Object Linking and Embedding was subject to backward incompatibility if embedded object such as XLS chart was of different version than the supported one, resulting in conversion issues. DOCX, on the other hand, can support both backward and forward compatibility due to its XML structure and conversion issues due to version difference can be easily handled.
  • Older formats such as DOC and XLS are prone to the attacks of malware due to binary nature of their file structure, resulting in becoming a source of spreading virus. This is not the case with DOCX as malicious binary code can not be injected inside the documents. 

How to Open DOCX on old Microsoft Word Versions

Microsoft Word 2003 or before can not open DOCX files. However, Microsoft provides a compatibility pack that can be installed and used to open the DOCX file format on older versions of Microsoft Word. In addition, there are free online converters available that can help convert files from DOCX to DOC file format.