One of the big mysteries inside the Ultima Online DAT file were the .m (.m.q) files. Those files, like the directory name suggests, contain code. As it turns out, the scripts are obfuscated but by analyzing the script execution engine inside uodemo.exe I was able to figure it all out.

More technical explanation can be found on the wiki :

There are 1615 scripts in total, 814 of them assign behaviours to objects. The other 801 are the behaviours themselves, the skills & dungeon scripts (quests). OSI magery is spread over more than 120 scripts (2 scripts per spell).

How to "decompile" the scripts:
1) Extract the "scripts" directory from the DAT file :
2) Download the Mass M Decompiler :
3) Run the "Mass M Decompiler" and point it to the "scripts" directory
4) Press the Dump All button when decompilation is complete

You will find that the variable names inside the scripts are obfuscated.

Nothing is changed.. Mass decompile button doesnt work.

Hello xantier

You have to press the "..." button and select the directory that contains the .m files & the sdb.txt file.

Screenshot Mass M Decompiler.JPG (100 KiB) Viewed 10009 times

If you have VB.Net installed (Express editions should work), set a break-point at the ScanAndDecompileAll procedure at see what happens there.

Link doesn't work for me.

I can't get the Mass Decompile to work either. I've selected the correct directory, but still nothing.

edit: Nevermind, I got it working after messing around with it in visual studio a bit.

Btw, thank you for all of this Batlin.

Now I just gotta figure out a way to re-compile the scripts. ;p

I've uploaded a new version of the Mass M Decompiler which fixes a bug that Garret reported me 9 months ago. Sorry for the delay.

To fix the bug manually in your already decompiled scripts: replace "location usedon" by "location place" in those scripts that implement the "targetloc" event.