KSI branched out into "rapping" around the same time the Sidemen formed. On the 26 October 2016, KSI embarked on his first European music tour, where he performed in the U.K., France, Germany, Netherlands and Belgium.
Due to certain fans complaining that KSI's music career had "taken over" his main YouTube channel, he decided to activate a VEVO channel. This has 3 videos and around 500,000 subscribers as of August 2017. KSI's VEVO channel, as of 2022, is unused with his official music videos being posted on his main channel.
KSI featured on a single by British rapper Sway, titled No Sleep. The song reached number 44 on the UK Singles Chart. The music video for No Sleep was released on KSI's YouTube channel on 20 October 2013.
On 23 March 2015, KSI released his debut single Lamborghini, which features British rapper P Money. The song reached number 30 on the UK Singles Chart, and remained his highest charting song until the release of Down Like That in November 2019.
Later on in 2015, KSI revealed that he was preparing to release his debut EP. The lead single Keep Up was released on 13 November 2015 and features British rapper JME. The song was originally scheduled to be released on 1 January 2016, but was brought forward due to the song's appearance on Now That's What I Call Music! 92. Keep Up peaked at number 45 on the UK Singles Chart. On 8 January 2016, KSI released his debut EP titled Keep Up. The EP reached number 13 on the UK Albums Chart.
In early 2016, KSI announced that he would be releasing his second EP, due to be released towards the end of 2016. The lead single Goes Off which features British-Ghanaian musician Mista Silva was released on 29 April 2016. However, the single failed to make an impact on the UK Singles Chart.
KSI released the EP's next single Friends With Benefits on 29 July 2016. The song features Dutch musicians MNDM and peaked at number 69 on the UK Singles Chart.
A new single titled Jump Around was released on 16 September 2016. The song features American rapper Waka Flocka Flame and samples the song Jump Around by House Of Pain. However, the single failed to make an impact on the UK Singles Chart. The music video for Jump Around was the first of KSI's music videos to not be released on his YouTube channel; Instead it was released on his newly established VEVO channel. KSI released his second EP titled Jump Around on 28 October 2016. However, the EP failed to make an impact on the UK Albums Chart.
When Joe Weller won his first amateur boxing fight in August 2017, KSI offered himself as his next opponent. After multiple press conferences and videos surrounding the "drama" that had arisen between the two, their official fight was confirmed.
On 3 February 2018, KSI and Joe Weller contested in an amateur boxing match at the Copper Box Arena in London, England. KSI defeated Joe by third round technical knockout (TKO).
Following his victory against Joe Weller, KSI called out both Logan and Jake Paul as his next opponents. After many disagreements and much uncertainty about whether the fight would happen and who KSI's opponent would be, the fight between KSI and Logan was officially announced on 18 March 2018. There were two press conferences for the fight; the first was in the US on the 16 June 2019 and the second was in London on the 18 July 2018.
On 25 August 2018, KSI and Logan Paul contested in an amateur boxing event at the Manchester Arena in Manchester, England. After six rounds, the fight resulted in a majority draw with two judges scoring it 57-57 and one judge scoring it 58-57 in favour of KSI.
As a result of the first fight being a draw, both KSI and Logan Paul agreed on a rematch. On 3 September 2019, the rematch was officially confirmed, along with the announcement that it would be a professional fight with no headguards, and that it would be promoted by Eddie Hearn. KSI officially registered as a pro boxer with a professional boxing license; he trained for the fight under his coach, Viddal, and Jeff Mayweather.
On 9 November 2019, the professional bout took place at the Staples Centre in Los Angeles, California. After six rounds, KSI was announced as the winner by split decision with two judges scoring 57-54 and 56-55 in favour of KSI, and a third scoring it 56-55 if favour of Logan.
KSI and Logan shared an embrace in the ring, and payed respects to one another. Logan announced that he had appealed the decision of the fight, however the appeal was denied in December 2019, assuring that KSI had won the fight.
On 23 June 2017, KSI posted a new video, entitled "It's been a while...", implying that his return to YouTube is imminent. Alongside posting that video, he also tweeted out about an upcoming EP, called Space. It was released on 30 June 2017.
Four days later (27 June 2017), KSI posted another video, his music video for the song Creature. It's the only song that has been released from the Space EP so far. It was previewed in the "It's been a while..." video, as the song appears to be heard in the background of the video.
The description of the video states "for Alfie". Alfie was a fan of KSI and Deji who was living with bone cancer. KSI and his brother visited Alfie prior to the release of the song (and gave him a shirt). It is very much thought that the video is dedicated to him.
It's been a while...
K.S.I - CREATURE
Alfie meets his heroes, KSI and Deji
Alfie meeting his true heroes KSI & Deji.
Disstracktions EP
At the end of "Adam's Apple", KSI revealed that he'd be compiling the disstracks into an EP called "Disstracktions". The EP was released in September 2017.
On 15 September 2017, KSI released his new song "Transforming". In the song, KSI raps about everyone not understanding him and not letting him be himself.
2018
Release of Uncontrollable
On 31 January 2018, KSI released his new song ''Uncontrollable''. As the title says, KSI raps that no one can control him. It was basically a teaser of the boxing match against Joe Weller. The song was used for his ringwalk on the day of the boxing match.
After over a year of not posting videos on his second channel, he posted an announcement vid on December 31 of 2018, announcing that he would return to posting regular content on his second channel.
Beef with MaximillianMus
Maximillianmus and he had a small beef in late January 2019, at the time Max released a song called "Oh Yeah Yeah" which throughout the song, repeated the phrase "Oh yeah yeah" a lot of times. The song went viral and hundreds of videos comment sections were being raided by people spamming "Oh yeah yeah" on them, one of the channels being KSI. KSI tried to stop this, since he thought it was ruining YouTube, by starting "Operation Blackout" where you would blackout your profile picture, and just spam "STOP" on all YouTube comment sections being raided by "Oh yeah yeah" comments. When he was doing a One Question Go video, Max managed to get in the server in time, and confronted KSI about Operation Blackout. The operation was a failure, so KSI surrendered and changed his profile pic to Max's except with a bandana temporarily, which fixed his comment section, and after a couple months the meme died down. It is assumed that the 'beef' was somewhat of a joke and that there is no actual drama between KSI and Max.
In 2019, he and Randolph begun working on an album together titled "New Age" that would have 10 songs on it, 3 of them being singles. The album was released on April 12, 2019 and reached Number 17 in the UK Albums Chart.
New Age Tour
Throughout May and July, he and Randolph went on tour to promote the New Age Album. They performed most of the songs from the New Age Album, but also played a lot of other songs from KSI's other albums like the Space EP, and Disstracktions too.
Boxing Match
It was revealed on September 3 that the KSI v Logan Paul rematch was taking place on November 9 in the LA Staples Centre. The fight, unlike last time, is a professional boxing match with no head guards.
The fight resulted in a win by split decision for KSI.
Press Conference
The press conference for the rematch took place on September 14 in the Gilbert Lindsey Plaza, LA.
On November 7th, 2019, just 2 days before the KSI V Logan Paul Rematch was held, KSI released a new single titled Down Like That, featuring American rappers Rick Ross and Lil Baby and British musician S-X. The song was used for KSI's ring walk during his rematch against Logan Paul, with live performances done by Rick Ross and S-X. A music video for the song was filmed on November 11th in Los Angeles and premiered on KSI's YouTube channel on November 22nd.
The song entered the UK Singles Chart at number 17 and peaked all the way up to number 10, becoming KSI's highest-charting single in the UK until it was surpassed by Houdini in April 2020, outperforming his previous highest-charting song, Lamborghini, which managed number 30. The song also managed to chart in - Billboard Hot 100 Canada, Ireland, Lithuania, New Zealand Hot Singles, Scotland, UK R&B and UK Indie.
On January 31, 2020, KSI released a single named Wake Up Call featuring American rapper Trippie Redd. The song debuted at 11 in the UK Singles Chart, making it KSI's third highest-charting single in the UK behind Houdini and Down Like That and his highest-debuting song before being surpassed by Houdini 3 months later.
Poppin
KSI released "Poppin" on 27 March 2020 as a single from his studio album, Dissimulation. The song features Lil Pump and Smokepurpp. It debuted at 43 on the UK Singles Chart, 23 on the UK R&B Chart and 4 on the UK Indie Chart. KSI created the "Poppin" challenge, in which people could send in their own verses and the winner's would be featured on the song in the deluxe version of Dissimulation. Crypt was voted as the best verse and won the challenge.
On 24th April 2020, KSI released another single named Houdini featuring British singer Swarmz and British Rapper Tion Wayne. The song charted at number 6 on the UK Singles Chart, making it his highest-charting single in the UK to date, outperforming his previous highest-charting song, Down Like That. It is also his highest-debuting song and his second song to reach the Top 10.
On May 23, 2020, KSI released his debut studio album Dissimulation, the deluxe version was released 3 days later on May 25, 2020. The album features artists such as Offset, Rick Ross, Lil Baby, S-X, Lil Pump, etc. Singles like Down Like That, Wake Up Call, Poppin, and Cap supported the album. The album reached #2 on the UK Albums Charts making it the highest debut album to reach in a short amount of time.
On July 24, 2020, the single Lighter by Nathan Dawe, featuring KSI, was released. The song charted at number 3 on the UK Singles Charts and has also won the Amazon Music UK award for best song of the year (2020). On January 1, 2021, the song was certified platinum by the British Phonographic Industry.
On October 23, 2020, KSI released a single titled Really Love featuring Craig David and Digital Farm Animals. The song, which is a track from him upcoming second album, charted at number 3 on the UK Singles Chart and stayed in said chart for 11 weeks. It has also been certified silver by the British Phonographic Industry.
On January 15, 2021, the single Don't Play was released by KSI, Anne-Marie and Digital Farm Animals. It is JJ's second collab with Digital Farm Animals. The song charted at number 2 in the UK Singles Charts making it KSI's highest ever charting song. It was certified silver by the British Phonographic Industry.
Patience is a single by KSI featuring Yungblud and Polo G released on March 12, 2021. The song, which is another single from KSI's upcoming second album, charted at number 3 in the UK Singles Chart and number 2 in the Billboard Euro Digital Song Sales chart.
Holiday is a solo track by KSI released on June 18, 2021. This is the fourth single from his upcoming second album ‘All Over The Place'. The song charted at number 2 in the UK Singles Chart.
Not Over Yet is a single by KSI featuring Tom Grennan released on August 5, 2022. The remix of the song was performed for KSI's ring walk in his boxing match against Luis Pineda.