But the old formats are also (mostly) documented by Microsoft. Only once did I have to reverse-engineer a magic number, and only to get something working with E

But the old formats are also (mostly) documented by Microsoft. Only once did I have to reverse-engineer a magic number, and only to get something working with Excel 97: http://phpexcel.codeplex.com/discussions/71551 http://phpexcel.codeplex.com/discussions/71551 For the most part, with Word I get better compatibility in LO with the old binary formats than with OOXML. If someone sends me .docx and it looks garbled, it's easier to ask them to resave as .doc than to try to get them to produce .odt