Day first became interested in music in 2005 when he bought an electric guitar at the age of 15. He started his YouTube account one year later on 4 August 2006. In 2008, Day founded Chameleon Circuit, a Trock (short for “timelord rock”) band that wrote music inspired by the British TV show Doctor Who. In June 2009, the band released its first self-titled album by YouTube musicians’ record label DFTBA Records and a second album Still Got Legs in July 2011. Wired noted that Chameleon Circuit “puts out titles that could pass for chart-toppers – if they weren’t excessively nerdy in the subject matter department.”

Alex Richard George Day was born in Hornchurch in the London Borough of Havering. Day grew up in Hornchurch, where he started his YouTube channel, nerimon, in 2006. He attended university but never received his degree, instead treating his independent music and video blogging as a full-time profession. He worked in the Regent Street Apple Store during 2009. Until 2013, Day used to live with friend, collaborator and bandmate Charlie McDonnell. In August 2010, Day briefly lived in Zambia whilst taking part in the World Vision Vlogger charity event. He filmed and shared his experiences on YouTube.

Day’s “disruptive distribution” strategy has been lauded as “the future of music”. In 2008 he was noted as one of the most successful and popular YouTubers in Britain at the time. Day has been profiled on BBC and CNN and in world publications like Forbes, The Guardian and Holy Moly.

Day released his debut album Parrot Stories in April 2009 through DFTBA Records, which was produced by fellow musician and friend Tom Milsom. This was then followed by an EP, 117% Complete, in March 2010 which contained songs referencing various video games such as Pokémon. His second album, The World Is Mine (I Don’t Know Anything), was released in June 2010 contained a more electronic-dance sound than his previous folk album. To ensure he did not alienate his fans of his debut album, Day released an EP of acoustic songs, Soup Sessions: Acoustic, in November 2010 which contained newly recorded acoustic versions of half the songs on the album.

Day was a featured artist on the BBC Two reality show Chartjackers in 2009. The programme challenged four YouTube video producers to write, record and release a pop song in 10 weeks, using YouTube as a tool to get lyrics and singers, with the proceeds going to the BBC Children in Need charity.

The completed single, entitled “I’ve Got Nothing”, was sung by vocalists Miranda Chartrand and Adam Nichols, and was released worldwide through the iTunes Store on 9 November 2009. It was reviewed with varying degrees of approval by various media outlets, including The Times, Yahoo! Music’s James Masterton, BBC Radio 1’s Chart Blog and Popjustice. The song peaked at No. 36 on the UK Singles Chart and raised almost £10,000 for Children in Need.

For Christmas 2011, Day released his single “Forever Yours”, which reached No. 4 in the UK Singles chart after selling over 50,000 copies in one week. Day released the single without support from a record label or TV coverage, and outsold songs from multi-platinum artists such as Coldplay, Rihanna, and Katy Perry. The Official Charts Company lauded Day’s success, stating ” ‘Forever Yours’ is certainly one of the most successful self-released tracks we have ever seen, the Official Charts are based on sales, and sales alone, so Alex’s achievements this week are a genuine reflection of the passion of his army of fans, and of course, the power of social media.” Day also released 11 alternate versions of “Forever Yours”, which he confirmed that all sales revenue made from the alternate versions would be going to charity, chiefly to World Vision.

On 1 April 2012, Day released his second single, “Lady Godiva”, a cover of the 1966 Peter and Gordon song. The single was Day’s first to get a physical release in UK record stores following a one-single distribution arrangement with HMV and other stores. Within its first week of release, the song charted at No. 15, making it Day’s second UK Top 20 hit. The song also charted in 15 other countries including Australia, New Zealand, Canada, the United States, Sweden, Norway, and Spain as well as reaching No. 1 in Slovenia. In May 2012, Day released three singles—”Good Morning Sunshine”, “She Walks Right Through Me”, and “This Kiss”—on a single day, selling nearly 150,000 copies. This “disruptive” model largely ignored the conventional method of releasing one single every few months, and its success was profiled in MTV and Billboard.

On 16 December 2012, he attempted to break a world record with his song “Stupid Stupid”. The song later peaked on UK charts at No. 25. In order to promote the single, Day held a one-day tour entitled Stupidfest, which was free for entry.

Day released his third album, Epigrams and Interludes, on 17 March 2013. It contains all his previously released singles since “Forever Yours”. He also released a music video for ‘I’ve Got What It Takes’ starring Tom Ridgewell, Carrie Hope Fletcher and Khyan Mansley. The album debuted at No. 2 on the UK iTunes charts.

In late 2013, Day announced that he had completed work on his first book; with the working title The Underground Storyteller, the book was about his experiences with the London Underground. It was 12 chapters in length and was scheduled to be published in July 2014. It was cancelled by the publishers. On 13 October 2014, Day announced online that he was releasing his book independently, keeping the name of The Underground Storyteller, and that he will sign and number the first thousand copies.

Day announced on 14 February 2014 that he had been dating fellow YouTuber Carrie Hope Fletcher since October 2013. However, Fletcher announced their break-up via Twitter on 14 March 2014.

Day originally identified as an atheist but began to follow Buddhist teachings after visiting the Plum Village Monastery in mid 2014. Day also identifies as a minimalist.

In March 2014, Day admitted to having engaged in “manipulative relationships” with some women and having “created situations that put people under enormous pressure”. He made further admission, saying, “the model of consent that I followed… was that only, ‘no’ meant, ‘no’. That is not what consent is”. He also announced via his blog that he had taken down his merchandise and artist pages from his label’s website.

On 5 October 2014, after a seven-month hiatus, Day released a statement regarding the allegations, claiming that he “didn’t realise at the time that [the women] felt pressured”, and apologising. In the half-hour video he also referenced what he saw as “militant” reactions posted on the social networking site, Tumblr, labelling them as “an angry torrent of abuse” and “people just being absolutely horrible to anyone who doesn’t agree with them”. His response was criticised by several YouTube contributors such as Laci Green, Jack Howard and Tomska.

In March 2014, Day removed his artist pages, merchandise and information from his record label, DFTBA Records following accusations of sexual manipulation. His official website alexdaymusic.com has also been taken down, the content being replaced with generic landscape photos.

On 5 October 2014, Day uploaded a video on his YouTube channel, his first video since February 2014. It was titled “The Past”. In the video, Day talks about his side of the allegations accused of him, as well as his thoughts and opinion on the matter. Day also mentioned that he planned on creating and uploading more videos talking about the situation.

Day further found success through a popular series of videos entitled Alex Reads Twilight, in which he read and critically analysed the popular young-adult novel Twilight, by Stephenie Meyer. The videos have received a total of over 14 million views. Amongst these, Day’s YouTube channel also contains travel vlogs, music videos and satirical rants. In June 2014, he had reached over a million subscribers and his videos had been watched over 100 million times.

Day’s return to YouTube in October 2014 was met with an extremely negative response, in particular his decision to monetise response videos to the sexual abuse allegations.

On 10 January 2015, Day uploaded his new single, “Scared Like Me”, to YouTube and thus announced his musical return. It was his first new song in two years. Day also announced that he would be releasing a new album on 4 October 2015 and throughout the year he would release three more singles from this album. It was later announced that this album would be called ‘Nowhere Left To Hide’.

On 3 April 2015, Day uploaded a new track to his channel, which was a cover of Chumbawamba’s Ugh! Your Ugly Houses!. It was intended as a protest single, to be released on the week of the 2015 UK General Election, focusing on the lack of representativeness of the UK government and electoral system. Day aimed for the single to chart at number 1 in the UK on the track’s week of release, however it failed to chart. He later announced that this song would not be part of his fourth album, but instead a cover album he would release at a later date.

On 17 May 2015, Day released a new single available to download on his website, entitled ‘Keep Me Up’. His fourth and final single, titled ‘Beyond You’ was released on 26 July 2015. On 3 October, Day announced he would release the album a day early for all of those who signed on for the newsletter. He also announced that rather than a physical CD edition, Nowhere Left To Hide would be released as a physical USB with the album on. On the album, Day stated ‘This was a hard album to make. In a lot of ways, it was an album I needed to make. It’s quite raw and makes me feel a bit exposed. But I love it and I’m very proud to have it and to share it. I think parts of it are my best work and overall it’s probably the most cohesive release I’ve ever put out’.

In December 2015, Day announced he had recorded five new songs for an untitled studio release in the future. On 28 January 2016 he confirmed the album would be called Split Infinities and would be the first of his solo albums to feature a backing band. He released it on 30 September 2016. Day released his sixth album Sunset on streaming platforms in October 2019. Day has now deleted his main channel Nerimon and a majority of his online presence to pursue a career outside of YouTube. He still creates content on Patreon.

In early 2015, Day stated that he was discontinuing his Nerimon channel in May 2015 after releasing what was then his final video on that platform, in order to set up a new channel entitled The Daily Day. In December 2015, Day announced his return to Nerimon. After dwindling success, Day retired and deleted the Nerimon channel. He eventually set up a patreon and continues to produce music, videos and content through donations.

On 10 May 2015, Day uploaded his final video to his Nerimon channel, entitled “Goodbye Nerimon” (last video!). Within it, he explained that he was launching a new YouTube channel called The Daily Day, which would feature a new vlog everyday, on different themes to his original channel. Day stated that the creation of a new channel was to “define a fresh start and have a channel focused on my new direction, with an active audience I know is there just for that”, and to clear out dead subscribers from the old channel after the loss of viewership.

Day’s second book was the memoir Living and Dying on the Internet, which detailed his personal experiences as a YouTuber and the controversies surrounding his sexual abuse allegations. During its conception and writing, Carrie Hope Fletcher threatened legal action in regards to her inclusion in the book. Though nothing came of this, Fletcher and many other YouTubers and ex-colleagues of Day spoke out against the release of the book and encouraged their followers not to purchase it. The book was released on 5 August 2018.

After a steady decline in viewers over the following years, in 2020 Day posted a final video to his channel, stating he would be moving away from his online presence as he was pursuing other employment. He has been inactive online since.