[Piskvorrr]

While XLSX is proprietary by descent, it is standardized; thus, it's readable/writable by man and machine alike (essentially a zipped XML with some bells and whistles). I have not encountered a less broken format that is similarly widespread.

[mark-r]

I don't think that's common knowledge, although I have unzipped a .xlsx file in the past to inspect the contents. Works on .docx files too.

P.S. Aren't .xlsx files subject to the same problem as the .csv?

[Piskvorrr]

Well, some of the issues are shared between CSV and XLSX. However, it does have a clear distinction between structure (which also can be validated!) and content (which moots the issue with comma-semicolon-tab separation), a well-defined character set and somewhat-sane character escaping rules.

It does have similar "executability" issues as CSV (and more), but 1. the formula evaluation is documented and expected behavior, 1b. there is a documented way to suppress it, and 2. programs reading it are aware that security is a thing, and either a) constrain/sandbox it (in the case of table processors such as MSOffice or LibreOffice), or b) don't execute its macros and expansions at all (in the case of libraries such as PhpExcel). Not sure about the Google Docs issue.

(As far as "common knowledge" - knowledge for manual inspection of strings is IMNSHO not required, all that's needed is that it's program-readable; in this respect, most table processors are capable of this. The point "but you can inspect CSVs by hand" comes from experience: it is also possible to inspect binaries by hand, neither of these is intuitive, both are a learned skill)