The .ditaotrc configuration file

As of DITA-OT 4.2, new files can be used to store DITA-OT runtime configurations in multiple places to support fine-grained configuration layers.

DITA-OT looks for .ditaotrc configuration files in the current directory or any ancestor directory first, then in the user’s home directory, and finally in the root directory of the DITA-OT installation. These files are read in order and combined with the contents of the local.properties file in the toolkit directory.

The first occurrence of a property takes precedence. This approach can be used to define multiple layers of configuration, so personal defaults that apply to multiple projects can be stored in the home folder, with local overrides in project folders.

For example, if the current directory includes a .ditaotrc file that sets 
pdf.formatter=fop
and the user’s home directory has a .ditaotrc file with the following content, 
pdf.formatter=xep
args.grammar.cache=no
DITA-OT will be run as if the following options were set on the command line: 
--pdf.formatter=fop --args.grammar.cache=no
Tip:
As of DITA-OT 4.2, any configurations in local.properties files should be migrated to .ditaotrc files.