A ONE file is a document created by OneNote, a note-taking program developed by Microsoft. It contains one or more sections made up of one or more pages of content. ONE files may contain text, digitized handwriting, and objects pasted from other applications, such as images, drawings, and audio/video clips.

ONE file open in Microsoft OneNote 2016 The ONE file is the main file type associated with OneNote. When you create a new notebook in the program a ONE file is automatically created and is automatically saved as you work. When you open a ONE file, the interface features a page where you can insert text, images, drawings, shapes, tables, and links. You can also choose to sync your ONE files in the cloud to keep them updated across all your devices. OneNote comes bundled with Windows 10 and is included with the Microsoft Office suite. It is also available for macOS, Windows Phone, Android, and iOS. The purpose of the program is to allow you to make typed or handwritten notes that can be shared with other users.