GRFCodec has moved

Development of GRFCodec is now in the hands of the OpenTTD team, you can find it here.

The older versions of GRFCodec can still be found below however.


A suite of programs to modify Transport Tycoon Deluxe's GRF files. Copyright © 2000-2006 by Josef Drexler.

This program is distributed according to the terms of the GNU General Public License, Version 2. For more information read the file "COPYING". This program can also be discussed on TTDPatch's mailing list.

Download it

Get the most recent GRFCodec toolset, version 0.9.10:

The source code is available from the TTDPatch Subversion repository (svn rev 819, http).

Note: If you use the script to renumber .nfo files, make sure to generate the .nfo file with the -t option to disable plain text strings. The script cannot deal with those correctly at the moment. Alternatively, try DaleStan's NFORenum tool.

Changes in 0.9.10 (r819): Changes in 0.9.9 (r653): Changes in version 0.9.8 (all by DaleStan): Changes in version 0.9.7: Changes in version 0.9.6 (all by pasky, not Josef): Changes in version 0.9.5: Changes in version 0.9.4: Changes in version 0.9.3:

Older versions available here.

GRF Wizard

GRF Wizard is a very useful Windows program written by Andrés Zsögön that takes care of using GRFCodec properly. It asks you a couple questions about what you want to do and then invokes GRFCodec for you.

Download it here!

How to use the programs

First of all, the programs are Windows console programs, which means that you must run them from the Windows command line prompt.

To install them, simply unzip the file into your TTD directory. All of the programs offer a brief description of their usage and options when called with the "-h" switch.

I also have the following documents available:

A tutorial on how to edit the GRF files
A brief summary of the usage and options of each program
A technical description of the GRF file format
A technical description of TTDPatch's new graphics files

Briefly, you use them like this:

To distribute your changes:

GRFCodec Files

These files are in
A program to convert GRF files into the common PCX format and back
Compares two GRF files and writes the differences into a GRD file
Takes a GRD file from grfdiff and merges the differences back into the GRF file
In addition, it also contains some documentation in text format:
A brief set of instructions on how to use the GRFCodec programs
A tutorial for editing GRF files using the GRFCodec programs
A technical description of the GRF format
The GNU General Public License, the terms under which GRFCodec is distributed
Note that the text files are also available in HTML format above.
Copyright © 1999-2006 by Josef Drexler.
Last changed on Nov 28 2006 16:33 EST by Josef Drexler