noun
helper application
In computing, an external program launched by a browser or other application to handle a specific type of content, such as a media player or PDF viewer.
ブラウザがPDFを表示するためにヘルパーアプリケーションを起動した。
The browser launched a helper application to display the PDF.
Borrowed from English 'helper application', a computing term for an external program that handles specific content types.