How to set the width of the columns

jojo____

Hi everybody,

I am trying to fix the width of the columns of my datatable but nothing changes and the datatable keeps calculating its columns.

I tried: "bAutoWidth" : false
And
"autoWidth": false

with: "columnDefs": [ { "width": "20%", "targets": 0 } ]
or:
"columns": [
{ "width": "20%" },
null,
null,
null,
null
]

But nothing makes the columns width change.

Thanks ;)