Turn a set of chapters into a real EPUB 3 file your reader can actually open β the job Vellum charges a couple of hundred pounds for and Designrr sells as a subscription. Write in plain text with light Markdown, add or generate a cover, then download a valid .epub built on your own machine. No upload, no account, no per-book fee, and no watermark in the file.
An EPUB is a zip file with a particular shape. The builder writes, in order and uncompressed as the format
demands: a mimetype file containing exactly application/epub+zip with no trailing
newline; META-INF/container.xml pointing at the package; then content.opf with the
Dublin Core metadata and the reading order; nav.xhtml as the EPUB 3 navigation document; a
stylesheet; and one XHTML file per chapter. Every entry gets a CRC-32, and the zip is assembled by hand β
there is no library here to do it.
Chapters are written in a small Markdown subset: #, ## and ### for
headings, - for bullets, 1. for numbered lists, > for quotes and
--- for a scene break. Inline **bold**, *italic* and
`code` are supported. Everything else is treated as a paragraph β which is the correct behaviour
for prose.
Your text is kept in this browser's local storage as you type, so a refresh does not lose the book. It is cleared by "Start over" and never leaves the device. Amazon's Kindle format needs a conversion step, which free tools do from EPUB; Apple Books, Kobo, Google Play Books and most readers open EPUB directly.