Estimated read time: 5-6 minutes
LEHI — As audiobooks rise in popularity, a team of Utah entrepreneurs is providing the world's first audiobook-filtering subscription service to allow listeners to enjoy popular books without offensive content.
Siftbooks is a service that helps audiobook listeners filter explicit content — including sexual scenarios, profanity and religious exclamations — out of audiobooks.
While print books remain the most popular way to read, 1 in 4 adults in the United States say they listened to at least one audiobook in 2021, according to Pew Research Center. In its May 2025 fiscal report, book publisher HarperCollins also reported a 3% increase in audiobook sales since last year.
As the demand for audiobooks climbs, the creators of Siftbooks hope their service will enable consumers to read the books they want without unwanted sexual or profane content.
Adam Coffey, one of the startup's founders, says the idea for Siftbooks began in 2022 when his friends and family were discussing the lack of regulation of offensive content in books.
"Movies and shows (have) ratings for everything," said Coffey. "There are also laws about what you play on the radio, what you play if you're in a store; basically, for the public or kids are around, there's certain rules about what can or can't be played. For other sorts of media, like audiobooks ... they don't have any sort of that information."
Most movies and TV shows receive content ratings based on age appropriateness from the Motion Picture Association's Classification and Ratings Administration and TV Parental Guidelines. The Recording Industry Association of America's Parental Advisory Label program is responsible for marking explicit songs and albums with an "E" to indicate potentially inappropriate content.
While some authors may choose to include content and trigger warning lists, books and audiobooks have no formal content rating system comparable to other forms of entertainment. This leaves consumers to rely on their own research or online reviews to understand how explicit the content may be or just leave it up to chance.
"There are many times more new audiobooks produced every year than there are shows or movies. It's not even close, the amount of, how quickly the content grows," said Coffey. "So, that being the case, a lot of people do get blindsided. It seems like in books and audiobooks, there is a bit more of a tolerance for what content is displayed."
Siftbooks aims to address this issue by offering a monthly subscription that connects with the user's Audible account and blocks explicit content in select books from their library. Listeners can tailor the filters to their personal preferences by choosing to block all types of explicit content or only certain types. Siftbooks offers a catalog of on-demand options that have already been filtered. Users can request up to one new book to be filtered each month, which typically becomes available within 48 hours, depending on the book.
With over 1 million books in its catalog, Amazon's Audible is one of the largest audiobook distributors on the market. While Audible is the only platform that works with Siftbooks, Coffey clarified that listeners are not required to have an active Audible subscription to use Siftbooks filters — they just have to own their audiobook on that platform.
"We're not selling audiobooks," said Coffey. "You have to verify that you have legal rights to listen to a book. So, on Audible, you have to own it. We validate that (users) have access through legal, valid means, and then we're simply just the tool that lays on top."
Siftbooks' filtering system is run by a machine learning model trained specifically using language found in books, according to Coffey. It works by muting or fast-forwarding through explicit content, which Coffey compares to a parent covering a child's eyes or using a remote to skip an offensive movie scene. On average, the system blocks about 95% of profanity and around 70% to 90% of sexually explicit scenes, since it can be more difficult to objectively determine what is considered explicit.
"This area can get very controversial very quickly," Coffey said. "There is a lot out there about moms fighting with school boards to get a book out of an elementary school library. Then there's the opposite group who feel equally passionate about that censorship ... you can see either side. So we're a little worried about the level of how polarizing this topic can be, but (ultimately) we're trying to see if we can reach the right audience."
Currently, the service is only compatible with Audible audiobooks, but Coffey says the team hopes to expand their service to be compatible with other distributors such as Libby, an app that allows consumers to digitally borrow e-books and audiobooks through their local library, as it grows.
Coffey said Siftbooks is often compared to VidAngel, another Utah-based service that allows users to choose to mute and fast-forward various types of explicit content in movies and TV shows. The Siftbooks team collaborated with some of VidAngel's founders while developing the audiobook service, aiming to avoid issues like the copyright infringement lawsuit VidAngel faced in 2016.
Still, Coffey says the threat of legal battles and other opposition from those who dislike content filtering services or altering the way readers consume content remains a concern.
"That's one fear we do have. Though we learn from VidAngel's lessons and know how to do it legally, compliant, there's always going to be the haters who don't want it to exist, and the creators get the final say," he said. "But at this point, we kind of have to make it or break it. We need to know if we can ... can we actually reach the target audience?
Siftbooks is available as a $10 monthly subscription. For more information, visit siftbooks.com.
