He was a member of the Iceland national team where he was capped 77 times and appeared at UEFA Euro 2016 and the 2018 FIFA World Cup.

Hannes played club football in Iceland for Leiknir, Afturelding, Stjarnan, Fram and KR.

[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.

[5] On 28 March 2012, Hannes joined Norwegian club SK Brann on a short-term loan, as a cover for injured goalkeeper Piotr Leciejewski.

[3] On 6 July 2015, Dutch Eredivisie club NEC announced they had signed Hannes on a two-year contract.

[21] Hannes made his international debut for Iceland in 2011, keeping a clean sheet in a Euro 2012 qualifier against Cyprus.

[22] At that time, Hannes was considered the main goalkeeper of the national team,[23] after appearing in all 12 2014 World Cup qualifiers for Iceland.

[26] He made his first UEFA European Championship appearance in matchday 1 of Group F versus Portugal which ended in a 1–1 draw.