[4] Williams made his senior début in the fourth round of the Challenge Cup in April 2013, scoring a try in a 60–10 victory over Championship club Leigh.

Following the departure of Blake Green, Williams became the first-choice stand-off for Wigan and was assigned the number 6 jersey before the start of the 2015 season.

Williams made 33 appearances and was a near ever-present throughout the season, missing only one game early in the year against Huddersfield after suffering an injury during the warm-up.

[11] On 19 February 2017, Williams was the stand-out performer in the 2017 World Club Challenge against National Rugby League Premiers Cronulla-Sutherland Sharks, helping Wigan to a 22–6 win.

[15] On 9 July 2019 it was announced that Williams would leave Wigan to join the Canberra Raiders for the 2020 National Rugby League season.

[18] On 22 June 2021, Williams fired one final parting shot at Canberra head coach Ricky Stuart saying “I'm just sad that relationship is pretty sour, I’ve not spoken to him since the release.

[21] In round 24 of the 2021 Super League season, he kicked two drop goals including the winner in golden point extra-time as Warrington beat Salford 20-19.

[25] In the 2024 elimination playoff against St Helens, Williams kicked the winning drop goal in Warrington's 23-22 golden point extra-time victory.

Williams played a total of 26 games for Warrington in the 2024 Super League season including their semi-final loss against Hull Kingston Rovers.

After an outstanding Super League 2015 season, Williams was selected in the England team for their test series against New Zealand.