The NFT auction marketplace OpenSea had a blockbuster 2021 and as a result is seeing its private valuation grow more quickly than almost any other startup.

The crypto firm announced late Tuesday that it closed a $300 million Series C round led by Paradigm and Coatue. The raise valued the startup at a massive $13.3 billion valuation, showcasing the wild growth the startup has seen in recent months. The Information first reported details on the Series C raise in November with Newcomer confirming additional details earlier today.

OpenSea saw more than $2.4 billion in transaction volume in the past 30 days alone, hauling in some hundreds of millions in fees last year. The firm’s ballooning valuation, which surged from a $1.5 billion valuation it was given just six months ago by Andreessen Horowitz’s crypto arm, is reflective of their own volume growth but also that of other flagship NFT firms including Dapper Labs, which raised at a $7.6 billion valuation last year.

In a blog post, OpenSea CEO Devin Finzer highlighted that his platform’s transaction volume increased “over 600x” last year.

OpenSea is firmly in the sights of dozens of other NFT marketplaces but has few major competitors at the moment, though that may change as Coinbase eyes the opportunity and other NFT marketplaces launch and receive funding. The NFT space saw plenty of action in 2021, but OpenSea realizing this valuation will rely on its continued success and its ability to entice newbies into the burgeoning world of crypto collectibles.