Replacement doesn't work as expected

[djsjo]

Problem

I have some lines with times like: 11:30 11:45 12:00 12:15

and wanted to replace them with the same value + a colon and a space.

Used Command

:%s/\v(\d{2}:\d{2})/\1: /gc

Expected Results:

The accordings lines are replaced with the colon counterpart. Tested in "real" vim and it works.

Actual Results

Tested in codemirror.net Getting the Information "No matches for \v(\d{2}:\d{2})" .