Cardiff have had winning runs of multiple games many times in their history but never a run of three victories from the start of the season.
So the class of 2017 are history makers and with three wins from three games, six goals scored and none conceeded the Bluebirds are top of the Championship.
Sean Morrison headed City into the lead a minute before half time, and after the re-start Cardiff were rampant. Chances came and went before Nathaniel Mendez-Laing scored another spectacular goal to extend the lead.
Sheff Utd pressed late on but the defence was superb again and Neil Etheridge was in fine form to deny the visitors a goal.
Two other sides have 100% records, Wolves and Ipswich, and next up for Cardiff is a trip to Molineux to face Wolves on Saturday (3pm).