Thanks for the tip, Sean. Looking back, I should have included "CSV" in the subject header of my post, but at the time I thought the issue my be something more than export format.

I agree this isn't related to encoding, it's best to stick to UTF-8. There is a hidden option to CSV and TSV Export "ForceDelimieters" that controls whether the setting for "TextDelimiters" is wrapped around text fields always, or only when needed. Since this isn't documented yet, this might change in future versions. The reason we always wrap non-numeric values in the delimiter is export would be much slower if it has to test each string for the presence of a comma, newline, or delimiter. Compare these outputs:

In[2382]:= ExportString[{{1, "B", "test,comma"}}, "CSV"]

Out[2382]= "1,\"B\",\"test,comma\"
"

In[2383]:= ExportString[{{1, "B", "test,comma"}}, "CSV", 
 "ForceDelimiters" -> False]

Out[2383]= "1,B,\"test,comma\"
"

In[2385]:= ExportString[{{1, "B", "test,comma"}}, "CSV", 
 "ForceDelimiters" -> False, "TextDelimiters" -> "'"]

Out[2385]= "1,B,'test,comma'
"

If your data does not contain any commas or newlines, then the best approach is to just disable text delimiters all together so that the string matching doesn't kick in (notice this mangles the field with a comma):

In[2387]:= ExportString[{{1, "B", "test,comma"}}, "CSV", 
 "TextDelimiters" -> None]

Out[2387]= "1,B,test,comma
"

P.S. I stumbled on this post by accident, and probably would have seen it sooner if CSV was in the title :)

Hi Rohit,

Thanks for the suggestion. I will compare the files in terminal, but see my response to Hans.

Regards,

Greg

Greg:

I tried a few things:

outs = Table[{RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}],RandomReal[{-10,10}]},{721314}];
Dimensions[outs]
{721314, 12}
Export["couts.csv", outs]

The file size without any options on my system is 155 MB (163,184,848 bytes) for this default Export. This is Windows 10 M 12.1. The file size is the same even with some additional options which M does not bark at:

CharacterEncoding -> "PrintableASCII", RecordSeparators -> "\r\n"

CharacterEncoding -> "ASCII", RecordSeparators -> "\r\n"

CharacterEncoding -> "ASCII", RecordSeparators -> "\n"

CharacterEncoding -> "UTF8"

CharacterEncoding -> "UTF-8"

"Export encodes line separator characters using the convention of the computer system on which the Wolfram Language is being run." From the Help files

The file size changed to 309 MB (324,927,070 bytes) when CharacterEncoding -> "Unicode" was used.

It could be the RecordSeparators or even quoted vs unquoted CSV format that may account for size dfference.

Hello Greg:

Please provide some sample code.

Using the Export and Import functions without options is asking for WRI magic to happen. In most cases this works very well if not even powerfull and keeps user from worry on/about details.

But without seeing any code on the Export and knowing what the default export options are on Apple Numbers, I would have to guess, ASCII, UTF-8, Unicode (character encoding) can account for the difference.

https://medium.com/@apiltamang/unicode-utf-8-and-ascii-encodings-made-easy-5bfbe3a1c45a

https://www.joelonsoftware.com/2003/10/08/the-absolute-minimum-every-software-developer-absolutely-positively-must-know-about-unicode-and-character-sets-no-excuses/