Born in Ålesund in western Norway, Grytebust was raised on the adjacent island of Ellingsøy. His father is a native of Ellingsøy and his mother is Liberian and Grytebust has described former Liberian international George Weah as his idol growing up. Grytebust did not originally play as a goalkeeper, but as a teenager deputised in goal when his team's goalkeeper was injured. A good performance led to him becoming the first-choice goalkeeper for the side. In 2004, aged 15 he was approached by Aalesunds FK, but chose to play for Ellingsøy IL's first-team in the Norwegian fourth tier before joining Aalesund's youth team one year later. After two season in the youth setup, Grytebust joined Aalesund's first team ahead of the 2008 season.
Club career
After joining Aalesund's first-team squad, the young Grytebust was the third-choice goalkeeper behind Adin Brown, Andreas Lie and later Anders Lindegaard who joined the side on loan. In August2009, after Lindegaard's loan-spell ended the team's coaching staff decided to give Grytebust his first team debut in place of Lie. He made his debut against local rivals Molde FK on 22 August 2009, and delivered a good performance despite conceding three goals. After his debut, Aalesund signed Lindegaard permanently and Lie left the team, leaving Grytebust as the second-choice goalkeeper for the following season. He played in the two first rounds of the 2010 Norwegian Football Cup. Grytebust was told by the club during autumn 2009 that he would be the next first-choice goalkeeper at the club. After the 2010 season, Lindegaard was bought by Manchester United and Grytebust was confirmed as the team's goalkeeper. Lindegaard stated that he believed Grytebust was ready for the task, and was certain that he would play for the Norwegian national side one day. The 2011 season started poorly with Aalesund losing against Fredrikstad partly due to a bad goal kick by Grytebust, but after his match-winning saves against Viking and Stabæk, the team's head coachKjetil Rekdal also predicted Grytebust would be the next national team goalkeeper. He delivered a stable performance throughout the season and was rewarded by being selected to the Under-23 national team together with his teammate Peter Orry Larsen, despite neither of them knowing that such a team existed. His performance also received praise from national team goalkeeping coach Frode Grodås who stated that Grytebust was "without weaknesses". After ending the season with a victory in the 2011 Norwegian Football Cup Final, Grytebust was named "Aalesund player of the year" by the local paper, Sunnmørsposten alongside Daniel Arnefjord. The 2012 season continued with Grytebust unchallenged as first-choice goalkeeper for Aalesund. Results varied and he received criticism when Aalesund were eliminated from the domestic cup in the fourth round against Sandefjord, with Grytebust being sloppy with a pass and conceding a goal. Later, during a match against SK Brann, he was again careless with a goal-kick, which ended with another goal conceded. In August the club reported that it had re-signed Andreas Lie as a back-up keeper, with Lie stating that he was keen to "play for a permanent spot". Grytebust left Aalesund in February 2016, joining Danish Superliga club Odense BK on a free transfer. He was voted Danish goalkeeper of the year in both 2017 and 2018 before joining FC København, again on a free transfer in May 2019, having opted not to sign a new contract at Odense.
