TreeLine is a free and simple outliner with advanced data element definition and export abilities. It uses a basic tree structure to organize information, and allows the user to define different types of nodes and leaves.
TreeLine outlines can be exported as HTML, per-data type user defined formatting. In addition, it supports exporting outlines as an OpenDocument ODT file, OPML, various delimited text file formats, and as "plain" XML.
TreeLine can import plain text, tab indented, delimited table files, Mozilla and XBEL format bookmarks, generic XML files, ODF text documents and older TreeLine formats.
TreeLine uses a simple JSON syntax to store data, with .trln extension. Versions before 3.0.0 used XML symtax with .trl extension.