IntelliJ Platform Plugin SDK Help

Registering a File Type

The first step in developing a custom language plugin is registering a file type associated with the language.

The IDE typically determines the type of a file by looking at its filename or extension.

A custom language file type is a class derived from LanguageFileType, which passes a Language subclass to its base class constructor.


When targeting 2019.2 or later only, use com.intellij.fileType extension point to register LanguageFileType implementation and instance via implementationClass and fieldName attributes. Also, name and language must be declared matching FileType.getName() and ID of language returned from LanguageFileType.getLanguage(), respectively.

To associate the file type in the IDE, specify one or more associations as listed in the following table.

Association type


Attribute value

Filename extension(s)


Semicolon-separated list of extensions, without . prefix

Hard coded file name(s)


Semicolon-separated list of exact (case-insensitive) file names

Filename pattern(s)


Semicolon-separated list of patterns (* and ?)

Hashbang (2020.2+)


Semicolon-separated list of hash bang patterns

To register a file type, the plugin developer provides a subclass of FileTypeFactory, which is registered via the com.intellij.fileTypeFactory extension point.


To verify that the file type is registered correctly, you can implement the LanguageFileType.getIcon() method and verify that the correct icon (see Working with Icons) is displayed for files associated with your file type.

Additional Features

If you want IDEs to show a hint prompting users that your plugin supports a specific file type, see Plugin Recommendations.

To control file type association with the IDE in the operating system, implement OSFileIdeAssociation (2020.3).

Last modified: 07 December 2023