[3] Williams spent the 2007 League of Ireland First Division season on loan at Drogheda United's County Louth rivals Dundalk.

[4] He spent the opening half of the 2008 season on loan from Drogheda United at Finn Harps following their promotion to the League of Ireland Premier Division in 2007 via the playoffs.

[4] His first goal came in the opening match of the season as Harps beat fellow Premier Division newcomers Cobh Ramblers 2–1 in Finn Park.

[4] He made his first team debut for the club on 20 July 2008, coming off the bench at halftime for Sami Ristilä in a 1–0 win over Cork City.

[4] Williams signed for League of Ireland First Division side Sporting Fingal and made his debut away to Waterford United on 7 March 2009.

[8] He scored 10 goals in 25 appearances in all competitions as his side finished 3rd in the league, beating Bray Wanderers 4–2 on aggregate in the Promotion/relegation play-off final.

[9] They also beat Sligo Rovers to win the 2009 FAI Cup with Williams playing the full 90 minutes of the Final at Tallaght Stadium.

[21] On 10 June 2022, Williams signed for League Two side Gillingham on a one-year contract,[22] reuniting with his former Millwall manager Neil Harris.

[30] Williams scored his first senior international goal for Ireland on 6 September 2018, after coming off the bench against Wales in the UEFA Nations League.