I have to put a file with some information (filename, content, time, sender, …) in a one-file package. That package will processed elsewhere.

The content of the original file can be binary as well as text.

Normally I would put the information in the filename and keep the content of the file as it is – but I think it is too much for this requirement.

What’s the best format/tech to do that?

I can think of XML, JSON, line-separated, keep the file and create an additional meta-file.

But maybe there is some better choice I did not think of for exactly that.