UTF-8 csv fix for Excel

Using utf-8 for your CSV files sounds obvious and works well in most software processing them.
Most software except Micrososft’s Excel, which, considering its number of users, can sadden your day.

Excel seems to assume windows-1252 unless a Byte order mark is provided.

To fix this without asking your users to navigate a maze of hidden menus, you can add a BOM to a string before saving it to a file or triggering a download.

In JavaScript:

let csvString = ["a,b,c", "1,2,3"].join("\n");
csvString = "\ufeff" + csvString;

or in PHP:

$csvString = implode("\n", ["a,b,c", "1,2,3"]);
$csvString = chr(0xEF) . chr(0xBB) . chr(0xBF) . $csvString;

If you look at the hex dump, you can check for the presence of this byte sequence at the very beginning: EF BB BF.