At 32 years old, JonTron has this physical status:
Jafari created a Newgrounds account under the name "BirdmanXZ6" in 2003, and uploaded five animations depicting anthropomorphic onions. In 2006, he made a YouTube account under the same name. Jafari uploaded videos on ScrewAttack.com in 2010, reviewing games such as GoldenEye 007 and at ScrewAttack, he met creator Austin "PeanutButterGamer" Hargrave.
On August 31, 2010, Jafari created a YouTube channel called JonTronShow. He stated that he chose the name JonTron because it was "reminiscent of technology" and that the show was originally going to be called JonTron 2.0. He uploaded a two-part review of the Nintendo 64 version of the game Daikatana, the first installment in his JonTron series. In each episode of JonTron, Jafari reviews singular games, as well as games of a particular theme, franchise, or genre. He is usually accompanied by his green-cheeked parakeet, Jacques, who speaks with a robotic voice. Jafari usually incorporates elements of sketch comedy into these episodes, to display his reactions to the video game that he is reviewing. According to Jafari, in an episode of the Internet gaming webseries Game Grumps, Jacques was originally to speak in a stereotypical jive voice, with Jafari's mouth being super-imposed onto the character's face, rather than his eyes glowing red whenever he talked. In his early days, he reviewed video games, showing fondness for Nintendo games and those developed by British game developer Rare mainly the games they made during the 90s, while being very critical of the games made since then like Star Fox Adventures and Banjo-Kazooie: Nuts & Bolts. Jafari has reviewed numerous video game adaptations of popular franchises, such as Hercules, Barbie, Home Alone, Star Wars and Conan the Barbarian, as well as relatively unknown games for the NES like Monster Party and Takeshi's Challenge. He has also reviewed various unlicensed games, particularly based on the Pokémon franchise, as well as the 1997 film Titanic and Disney films. In the latter, he observed China as being "farther away from U.S. jurisdiction, and much better at Disney bootlegging" and also remarked on unofficial online games based on the company's films. Jafari occasionally uploads skits, as well as film reviews. For his Halloween Specials, he reviewed the anthology horror television series Goosebumps and Are You Afraid of the Dark?.
According to Jafari, in an episode of Game Grumps, JonTron began achieving notability after a post on Reddit featuring Jafari's review of the Super Nintendo Entertainment System game DinoCity reached #1 on the website. In 2011, Jafari created two now-defunct spin-off Let's Play channels. The first, "JonTronStarcraft", has two videos of Jafari playing Blizzard Entertainment's real-time strategy game StarCraft. The second channel, "JonTronLoL", has four videos of Jafari playing the MOBA game League of Legends. Both channels have fewer than 25,000 subscribers. JonTronShow reached 1 million subscribers in May 2014.
In 2013 Paul Tamburro of CraveOnline said "Mixing a large dollop of offbeat humour with a light sprinkle of insightful commentary, JonTron's reviews of games of old have inspired many imitators, but none have proven to be more hilarious." Time magazine listed JonTron as 2015's seventh most searched Internet meme on Google.
In May 2015, Jafari released a spin-off web series on his YouTube channel titled JonTron's StarCade, in which he reviews games based on the Star Wars franchise. The webseries included cameos from numerous other Internet personalities and actors, such as Egoraptor, Markiplier, Nathan Barnatt, Ross O'Donovan, and Kyle Hebert. The series was produced by Maker Studios, a subsidiary of The Walt Disney Company, and concluded in December 2015, after nine episodes.
Jafari occasionally uploads videos in which he comments on matters that he finds important, which are usually related to gaming. This occurred most recently in 2016, with a video made in response to Blizzard Entertainment shutting down private servers of the massively multiplayer online role-playing game World of Warcraft. Jafari mostly criticized the shutdown of one of the most popular private servers, Nostalrius, which was a copy of the 1.12 version of the game. Jafari's video helped to raise awareness on this subject, and lead to thousands of signatures on a Change.org petition.
Throughout 2019 and 2020, Jafari has continued to broaden the range of media covered on his show, instead of solely traditional video games. Notable examples of topics are Flex Tape, rapper Soulja Boy's SouljaGame console, actress Gwyneth Paltrow's company Goop and its web series The Goop Lab, actor Dan Aykroyd's Crystal Head Vodka brand, and the 2007 TV series Kid Nation.
JonTron is largely credited with public awareness of Flex Tape and Phil Swift, and its transformation into an internet meme. The original video on the subject has received over 66 million views as of October 2021, and the sequel has over 26 million, and features a cameo from Swift himself.
NormalBoots was created in late 2010 by Jafari and Austin "PeanutButterGamer" Hargrave to act as a hub where Jafari and Hargrave could post content and receive advertisement revenue. Soon after its creation, Indie Games Searchlight and Cold Morning joined the group. In June 2011, the YouTube channel Continue? joined, while in August of the same year, Underbelly joined. In October 2011, Cold Morning left, and in June 2012, Underbelly left. However shortly after each departure new YouTubers joined, with The Completionist joining in November 2011, and Did You Know Gaming? joining in July 2012. The site was closed down in November 2012, as Google's AdSense program offered better revenue options for the content creators. Normal Boots was relaunched on January 24, 2014, so that the members could upload videos that weren't "YouTube friendly". Jafari alongside the remaining members of NormalBoots, apart from Indie Games Searchlight, came back, with two new YouTubers joining, ProJared and Satchell Drakes. On May 17, 2017, the group announced that they were going to reconnect due to the creators drifting apart. A new YouTube channel was created to unite the creators. During this time Jafari decided to leave to focus on his own channel but would still remain as a founding member.
Jafari met animator Arin "Egoraptor" Hanson, of whom he had been a fan since the early 2000s, when the latter messaged him on YouTube shortly after his review of DinoCity grew popular. The two eventually became close friends, and in July 2012, Jafari and Hanson announced they would be starting a Let's Play series titled Game Grumps through videos on both their channels. On July 18 of the same year, Jafari and Hanson uploaded their first serials of Game Grumps: Kirby Super Star, Mega Man 7 and The Legend of Zelda: A Link to the Past. On the Game Grumps channel, Jafari and Hanson played games together, typically ones that were retro or nostalgic in style, and commented over them with their own comedic inputs. On June 25, 2013, it was announced that Jafari had left Game Grumps in order to focus on JonTron, and was replaced by Ninja Sex Party singer Dan Avidan on the same day. The announcement was met with backlash by certain fans for its sudden and unexpected announcement without any lead-up, as well as the channel announcing the debut of the spin-off series Steam Train on the same day that Jafari's departure was disclosed.
Jafari has collaborated with multiple YouTube channels, including Ethan and Hila Klein's channel h3h3Productions. From October 2015 to August 2016, Hila Klein was a producer for JonTron. He has made an appearance on James Rolfe's Let's Play series James & Mike Mondays. He made a cameo appearance in Angry Video Game Adventures. Jafari was a featured vocalist in an episode of The Gregory Brothers' viral webseries Songify the News. At the same time, The Gregory Brothers remixed Jafari's review of the bootlegged game, Titenic, and it was released on iTunes.
Jafari has done voice-over work for Did You Know Gaming?, covering episodes on The Legend of Zelda, Banjo-Kazooie, Donkey Kong, Pokémon, Pikmin, Animal Crossing, Dragon Quest, Sonic Boom: Rise of Lyric, and games of Disney franchises. He has covered the development of Star Wars for their spin-off series Did You Know Movies? on fellow YouTube channel, The Film Theorists.
In 2013, before his departure from Game Grumps, Jafari and Hanson appeared in a promotional video produced by Polaris for the Warner Bros. movie Pacific Rim. Around the same time, Jafari appeared in Ninja Sex Party's music video for "Let's Get This Terrible Party Started", which was directed by Hanson. To promote the 2013 World Series, Jafari appeared in an a cappella cover of "Take Me Out to the Ball Game", produced by PepsiCo and musician Mike Tompkins, and uploaded to Maker Studios' Maker Music channel.
In November 2016, Jafari released an album called Love Is Like Drugs with The Gregory Brothers, which reached number two on the Billboard chart of comedy albums of the week of November 26. Later, on December 2, 2018, he collaborated with pitchman Phil Swift in the video "Flex Tape II: The Flexening".
Jafari played Banjo-Kazooie in June 2014 on a Twitch stream, to collect donations for Teach For America's GoFundMe campaign. Jafari stated that if the $25,000 proposed goal was hit, he would reprise a cover of Katy Perry's song "Firework" originally recorded for his 2011 review of DinoCity. The full version of the cover was uploaded to Jafari's YouTube channel on February 14, 2016.
In 2016, Jafari was featured as a character alongside other NormalBoots collaborators in the dating sim and visual novel Asagao Academy.
Jafari has provided voice-over work for A Hat in Time, a video game by Gears for Breakfast. He also recorded voice work for Playtonic Games' 3D platforming video game Yooka-Laylee, but the content was removed from the game in a day one patch, in light of his controversial statements on race (see § Political views and controversy).