Extract text from Book Designer files (HTML0)
To convert HTML0 files to another format, you need Book Designer or other E-Book software.
To convert other file formats to the "Legacy Project File" file type, you need software like Book Designer or a similar tool.
The .html0 file is an internal working format generated by Book Designer, a legacy Windows application once popular for creating and formatting eBooks. Authors used this software to import raw manuscripts and output older eBook formats like FictionBook (FB2), Rocket eBook (RB), or Sony Reader (LRF) formats.
Because Book Designer is now obsolete, the .html0 format comes with significant disadvantages. It is strictly an intermediate project file and is not meant for final distribution. You cannot upload an .html0 file to modern digital publishing platforms like Amazon KDP or Apple Books. While the file fundamentally contains standard markup, all styling is embedded directly inline rather than using modern, external CSS. This makes the underlying code dense and difficult to edit manually.
If you have old manuscripts trapped in this format, your best option is to convert them to HTML, EPUB, or PDF. Standard online converters often fail to process .html0 files because they rely on file extensions to determine the format; they do not recognize the rare "0" at the end and immediately reject the upload.
Convert.Guru analyzes your HTML0 file, detects the exact format, and lets you read the text inside.
If you want to convert HTML0 file to , you can use Book Designer or similar software from the "eBook Project Storage" category. In the File menu, look for Save As… or Export….
To convert files to HTML0, try Book Designer or another comparable tool in the "eBook Project Storage" category.
The history of Convert.Guru began over 25 years ago in California with Tom Simondi’s file-format database. A former contributor to Space Shuttle development and a software pioneer of the 1980s, Simondi established a trusted resource for file type analysis that was even referenced by Microsoft Windows XP. Today, we use modern technology to process and convert thousands of file formats while continually improving our HTML0 converter.