Williams studied Film & Television at University of Wales, Aberystwyth, before moving to Cardiff and launching the independent music magazine Kruger in 2003. Halfway between a fanzine and a magazine, and with good design at its core, Kruger was a mix of music reviews, interviews with interesting angles and features about music and culture. Kruger closed in April 2010. Williams joined NME as Features Editor in September 2010, was promoted to Deputy Editor in July 2011, and replaced Krissi Murison as Editor in June 2012. In 2015 he led NME through the biggest change in its history when he relaunched the magazine as a free title, delivering the highest ever circulation for the brand at 307,217. Williams was named Editor Of The Year at the BSME Awards 2016 for his work on the NME transformation, with the judges stating that under Williams' leadership, NME had "bounced back from an uncertain future and established itself confidently and creatively in a new market." During the United Kingdom general election of 2017, Williams was praised for his work in re-politicizing NME. Williams interviewed Jeremy Corbyn for the cover of NME, a move that was widely seen as a key factor in engaging young people in the election. In the interview, Corbyn pledged to "deal with" historic student debt. Williams stepped down from his position on 26 February 2018, stating "I leave in the knowledge that NME matters again, that it sets the agenda again, and that it's doing exactly what it always should again: turning the young people of Britain onto the music that's going to change their lives." In March 2018 it was announced that the NME was to cease publication in print after 66 years. The online publication would continue. In March 2019, Williams joined Time Out as Interim Editor. In July 2019 it was announced that Williams would become the new Editor in Chief of Sight & Sound, replacing departing editor Nick James who had been in the role since 1997.
In March 2017, the NME, then edited by Williams, used a photograph of British rapper, singer and songwriter Stormzy on its frontpage along with the headline, "Depression: It's time to talk". Stormzy responded on Twitter saying, "You lot know I don't rant or open my mouth up for no reason but serious @NME magazine are the biggest bunch of sly, foul PAIGONS" and "using my face as a poster boy for it to sell your magazine is so foul and below the belt I will never respect you lot." He also said, "You lot are a bunch of real life fucking pussyholes. Proper dickheads” and claimed that the NME had been "begging" him to be on the cover but he had "refused". According to The Guardian, "the phrasing of the NME cover created the impression the magazine had interviewed him, which it had not". A feature in the magazine instead used quotes from Stormzy taken from a different interview. Andrew Trendell, the journalist who wrote the feature, said he "had absolutely no part in the cover itself, the photos used nor the cover lines." However, responding to Stormzy via the NME's official Twitter account, Williams said, “I'm really sorry this has happened. We're a free magazine and were not trying to shift copies, just talk about something important.” Stormzy replied saying, "DEAD. You're NOT a non-profit organisation. The more copies you dish out the more you charge for advertising. You will make money from this". While Perez Hilton, founder of the Perez Hilton website, interjected to tell Williams, "this response is wack!!" Stormzy later referenced the incident on the song One Second from his album Heavy is the Head saying, "The cover of the NME, that shit made me resent myself. There's people tryin' to spread the word and people that pretend to help."
