LibreOffice Calc saves all the sheets of a Calc document together as an HTML document. At the beginning of the HTML document, a heading and a list of hyperlinks are automatically added which lead to the individual sheets within the document.
Numbers are shown as written. In addition, in the <SDVAL> HTML tag, the exact internal number value is written so that after opening the HTML document with LibreOffice you know you have the exact values.
To save the current Calc document as HTML, choose File - Save As.
In the File type list box, in the area with the other LibreOffice Calc filters, choose the file type "HTML Document (LibreOffice Calc)".
Enter a File name and click Save.
LibreOffice offers various filters for opening HTML files, which you can select under File - Open in the Files of type list box:
Choose the file type "HTML Document (LibreOffice Calc)" to open in LibreOffice Calc.
All LibreOffice Calc options are now available to you. However, not all options that LibreOffice Calc offers for editing can be saved in HTML format.