Hulu has repurchased AT&T's 9.5 percent stake in the business for $1.43 billion, giving the streaming company a valuation of $15 billion.

The transaction, announced on Monday, indicates that Hulu continues to gain popularity, even as the market for over-the-top content becomes increasingly crowded. The valuation is a big step up from November, when Disney said in a regulatory filing that the company was worth $9.26 billion.

Hulu is owned by a group of media companies, including Comcast, which owned 30 percent of the company before today; and Disney, which owned 60 percent, including 30 percent gained in its recent acquisition of Fox.

AT&T said it will use proceeds of the transaction to reduce its debt. AT&T purchased Time Warner last year, giving the company ownership of HBO, which has its own streaming offerings.

Disclosure: Comcast owns NBCUniversal, the parent company of CNBC.