Seventeen-year-old Ash has been living with her mother in her mother's boyfriend's house, along with his daughter Mimi and son Noah. When Ash's mother dies, Ash stays so she can attend a high school with a top coding program. But her stepsiblings take advantage of Ash's precarious living situation, with Mimi posting embarrassing pictures of Ash online and Noah making her do his homework. Ash's only solace is the social media app she has developed to support people who are being bullied online.
Using the handle Cinders, Ash starts chatting online with a girl who calls herself Charming. They become close, without ever meeting in person. When Ash finds out that Charming is Char, an aspiring singer who goes to her school, she admires her courage in identifying herself as a lesbian and singing about it. Char helps Ash see her own strength in not letting her situation cause her to be bitter, but instead using it to reach out to help others. For the first time since her mother died, Ash feels like someone sees that she is special and is there for her.
With a modern version of Cinderella as the main character, Cinders tells the story of a teen girl who overcomes adversity and bullying with kindness and compassion.