Sigil is a cross-platform EPUB ebook editor. It provides full support for the EPUB 2 specification and is currently being extended to support EPUB 3 as well. Sigil itself offers source code editing and a preview view, but a companion application called PageEdit can be installed to also provide WYSIWYG editing features. Sigil is able to import documents from plain text and HTML format, with automatic syntax checking and code cleanup available as optional steps in the import process. The FlightCrew plugin can be used to ensure that the documents produced comply with all the requirements of the EPUB standards. The Sigil GitHub site provides installers for Windows and macOS systems. Linux and BSD users can locate Sigil installers in their system's package repositories.