An Analysis of MDX/MDD File Format

MDict is a multi-platform open dictionary

which are both questionable. It is not available for every platform, e.g. OS X, Linux. Its dictionary file format is not open. But this has not hindered its popularity, and many dictionaries have been created for it.

This is an attempt to reveal MDX/MDD file format, so that my favarite dictionaries, created by MDict users, could be used elsewhere.

MDict Files

MDict stores the dictionary definitions, i.e. (key word, explanation) in MDX file and the dictionary reference data, e.g. images, pronunciations, stylesheets in MDD file. Although holding different contents, these two file formats share the same structure.

MDX File Format

MDD File Format

Example Programs is an example implementation in Python. This program can read/extract mdx/mdd files.

NOTE: python-lzo is required to read mdx files created with enegine 1.2. Get Windows version from

It can be used as a command line tool. Suppose one has oald8.mdx and oald8.mdd:

$ python -x oald8.mdx

This will creates oald8.txt dictionary file and creates a folder data for images, pronunciation audio files.

On Windows, one can also double click it and select the file in the popup dialog.

Or as a module:

In [1]: from readmdict import MDX, MDD

Read MDX file and print the first entry:

In [2]: mdx = MDX('oald8.mdx')

In [3]: items = mdx.items()

In [4]:
 '<span style=\'display:block;color:black;\'>.........')

mdx is an objectt having all info from a MDX file. items is an iterator producing 2-item tuples. Of each tuple, the first element is the entry text and the second is the explanation. Both are UTF-8 encoded strings.

Read MDD file and print the first entry:

In [5]: mdd = MDD('oald8.mdd')

In [6]: items = mdd.items()

In [7]: items =

mdd is an object having all info from a MDD file. items is an iterator producing 2-item tuples. Of each tuple, the first element is the file name and the second element is the corresponding file content. The file name is encoded in UTF-8. The file content is a plain bytes array.