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NML NewGRF meta language

NML is a a python-based compiler, capable of compiling NML files (along with their associated language, sound and graphic files) into grf and / or nfo files.

The documentation about the language can be found on

NML is licensed under the GNU General Public License version 2, or at your option, any later version. For more information, see LICENSE (GPL version 2), or later versions at

Table of Contents

  1. Contact
  2. Dependencies
  3. Installation
  4. Usage
  5. Reporting bugs and contributing

1) Contact

2) Dependencies

2.1) Required dependencies

NML requires the following 3rd party packages to run:

2.2) Optional dependencies

To install NML you'll need these 3rd party packages:

  • gcc (or possibly another c++ compiler). Needed to compile the cython version of the lz77 module for grf encoding.

Running make test requires these code formatters and checkers. You don't need these to use NML, only to test or help improve it.

  • flake8 Minimal version is 3.7.
  • black

3) Installation

The easiest way to install NML is by using pip:

pip3 install nml

In order to install NML from a source checkout run:

python install

If you want to install the package manually copy 'nmlc' to any directory in your path and the directory 'nml' to any directory in your python path.

4) Usage

Usage: nmlc [options] <filename>.

Where <filename> is the nml file to parse.


    --version             show program's version number and exit
    -h, --help            show this help message and exit
    -d, --debug           write the AST to stdout
    -s, --stack           Dump stack when an error occurs
    --grf=<file>          write the resulting grf to <file>
    --md5=<file>          Write an md5sum of the resulting grf to <file>
    --nfo=<file>          write nfo output to <file>
    -M                    output a rule suitable for make describing the
                          graphics dependencies of the main grf file (requires
                          input file or --grf)
    --MF=<file>           When used with -M, specifies a file to write the
                          dependencies to
    --MT=<file>           target of the rule emitted by dependency generation
                          (requires -M)
    -c                    crop extraneous transparent blue from real sprites
    -u                    save uncompressed data in the grf file
    --nml=<file>          write optimized nml to <file>
    -o <file>, --output=<file>
                          write output(nfo/grf) to <file>
    -t <file>, --custom-tags=<file>
                          Load custom tags from <file> [default:
    -l <dir>, --lang-dir=<dir>
                          Load language files from directory <dir> [default:
                          The default language is stored in <file> [default:
    --start-sprite=<num>  Set the first sprite number to write (do not use
                          except when you output nfo that you want to include in
                          other files)
    -p <palette>, --palette=<palette>
                          Force nml to use the palette <pal> [default: ANY].
                          Valid values are 'DOS', 'WIN', 'ANY'
    --quiet               Disable all warnings. Errors will be printed normally.
    -n, --no-cache        Disable caching of sprites in .cache[index] files,
                          which may reduce compilation time.
    --cache-dir=<dir>     Cache files are stored in directory <dir> [default:
    --clear-orphaned      Remove unused/orphaned items from cache files.
    --verbosity=<level>   Set the verbosity level for informational output.
                          [default: 3, max: 4]

5) Reporting bugs and contributing

5.1) Reporting bugs

If you find any bugs with NML, please let us know via the GitHub issue tracker. Please make sure that you're using the latest available version before reporting a bug. You can check the issue tracker to see if the bug you've found is already reported (or fixed!).

If you have bug fixes or other patches for NML, please also share those with us via the GitHub pull request page.

5.2) Making an NML release

  1. Check that all relevant PRs are approved and merged.
  2. Decide what the version number will be.
  3. Update the changelog. This is done manually, and commits are grouped by type. The audience is NewGRF authors and downstream package maintainers, so don't list commits that don't affect those audiences. For large releases and/or if there are deprecations or nml syntax changes, provide more detailed release notes. Example:
  4. Publish a new release using the release tool in the GitHub project:
  5. GitHub Actions will build the release, publish to PyPI (the Python package index) and also to the GitHub release.
  6. GitHub Actions will publish the Windows binary to the GitHub release.
  7. (Optional) announce the release in places such as