When speaking of "file format standards" or "data format standards" (Not standard methodologies), there are another 2 concepts that mix with "Standard":
(1) "frequently used data format" or "frequently used file format"
This case, is a data / file format that is commonly used, sometimes has subbranches, but is not regulated by a organization to be considered a standard. I believe JSON started like this, and eventually became a standard.
(2) "open, not frequently used, data format" or "open, not frequently used file format"
PDF started like this. Some programmers used PDF, but did not know its internals. Later, Adobe "opened" the format and it became available, even if it wasn't commonly used. The same goes for the PNG image format.
So, in theory you may create your own data / file format, expect it to become commonly used, and later become standardized by an organization.