Became an Oscar nominee at age fourteen for her role in the 2010 film True Grit. In 2015, she appeared in Pitch Perfect 2 and later starred in The Edge of Seventeen and Bumblebee. Also a singer, she released her debut EP Haiz, featuring the single "Love Myself," in 2015.
She began acting in short films at the age of eight. She was homeschooled from age 11 through high school.
In 2013, she starred as Juliet Capulet in Romeo and Juliet and played Petra in Ender's Game. She also provided her voice for the 2018 animated film Spider-Man: Into the Spider-Verse.
Her parents are Cheri and Peter Steinfeld and she has an older brother named Griffin. She dated Niall Horan in 2018 and dated Cameron Smoller in 2017.
She appeared in Taylor Swift's music video for "Bad Blood" in 2015.