Hannes joined KR at the age of 5.[3] He quit football at the age of 20 following a shoulder injury, before returning to the sport and joining third-tier Leiknir.[3] Hannes started his career at Leiknir at a time when the team was in the fourth- and third tier of the Icelandic football league system.[4][5] Hannes was let go from Leiknir in 2004 after making a number of serious mistakes in an important game that revolved around progressing to the second tier.[4]
During his time at Leiknir, Hannes sought to join Númi, which played in the Icelandic bottom tier, after struggling to get into the Leiknir first team, but the team rejected him.[6][5] After leaving Leiknir, Hannes joined Afturelding, which played in the third tier.[7]
Early in his career, Hannes struggled with shoulder injuries.[5] Hannes was known for poor kicking during his early career.[8]
In 2006, Hannes joined Stjarnan, which played in the second tier.[5]
Hannes said that at the time (in early 2005), he set a goal of becoming a goalkeeper for a team in the first tier in three years' time, and hoped to play abroad after that.[7]
He joined KR in 2011, winning the double with the team in his first season.[5]
On 28 March 2012, Hannes joined Norwegian clubSK Brann on a short-term loan, as a cover for injured goalkeeperPiotr Leciejewski.[9]
In December 2013, Hannes joined Norwegian clubSandnes Ulf, having trained with the club in October 2013 as preparation for Iceland's World Cup playoff game against Croatia.[10] He became a professional footballer in 2014.[3]
On 6 July 2015, DutchEredivisie clubNEC announced they had signed Hannes on a two-year contract.[11]
On 15 July 2016, Danish clubRanders FC signed Hannes on a three-year contract.[12]
On 3 July 2018, Hannes signed a two-year contract withQarabağ FK.[13][14][15] On 5 April 2019, he left Qarabağ by mutual consent.[16] Hannes had at that point become the third-choice goalkeeper at Qarabag.[17]
On 9 April 2019, Icelandic clubValur signed Hannes on a four-year contract.[18] Hannes cited family reasons and the four-year contract as reasons to return to the Icelandic top flight division.[17] He left Valur on 11 November 2021.[19]
On 16 March 2022, Hannes announced his retirement from football.[20]
In June 2022, Hannes agreed to joinVíkingur Reykjavík as backup goalkeeper following the injuries of Víkingur goalkeepersIngvar Jónsson and Uggi Auðunsson.[21]
Hannes was selected forEuro 2016, Iceland's first ever appearance in a major international football tournament.[26] He made his first UEFA European Championship appearance in matchday 1 ofGroup F versusPortugal which ended in a 1–1 draw.[27] Iceland eventually reached theknockout phase after finishing runner-up behindHungary.[28][29][30]
Hannes has worked as a film director when not playing football.[3][35] He directed, amongst other things, Iceland's video for their entry to the2012 Eurovision Song Contest.[36] His employer before leaving to Norway to become a fully professional footballer,Sagafilm, has promised him his job back when he returns to Iceland after his expatriate footballing career.[37]