Mixer, originally called Beam, was acquired by Microsoft in 2016 and renamed in 2017.

Niles Heron, an executive at Loaded, Mr. Blevins’s management company, declined to comment on how much Mr. Blevins was being paid as part of the deal, but said that “the decision was overwhelmingly not driven by the monetary value.”

Mr. Heron said the opportunity to attract new viewers was a consideration in Mr. Blevins’s move. Mixer, with its direct connection to Xbox — both are owned by Microsoft — has a generally more youthful audience because younger gamers are more likely to play on consoles than personal computers, he said.

“It was clear that it was the right time to open new doors that let Tyler define his lane,” Mr. Heron said. “Xbox is the dominant console of the day and Windows is the platform of Halo, the first game he played as a professional gamer. It made a lot of sense.”

Twitch wished Mr. Blevins luck in his future endeavors. “We’ve loved watching Ninja over the years and are proud of all that he’s accomplished for himself and his family, and the gaming community,” the company said in a statement.

Mixer said in a statement: “We’re thrilled to welcome Ninja and his community to Mixer. Mixer is a place that was formed around being positive and welcoming from day one, and we look forward to the energy Ninja and his community will bring.”