.OO3 File Extension

Data file created by OmniOutliner, a program used for organizing information; can store information using text, checkboxes, pop-up lists, and spreadsheets; used for various purposes, including note taking, tracking expenses, and creating agendas.

OO3 files can be exported to a variety of text and document file formats, including .KEY, .DOCX, .RTF, .TEX, .OPML, and .HTML.