Sigil is a free and open source ebook editing software for Windows, macOS and Linux. Using this you can edit books in ePub format. It supports both ePub 2 and ePub 3 file formats. It is based on QtWebEngine and released under GNU General Public License v3.0. It comes with full full UTF-16 support, code view and preview view, metadata editor, Spell checking and you can extend the features of Sigil with plugins. Some other useful features are diect editing of EPUB syntax in code view and comes with build-in table of contents generator with multi-level heading support.