None, as it doesn't have one. It uses a different DTL architecture called a Directed Acyclic Graph (DAG), known as The Tangle.

A blockchain is a DAG. Just one with no branches. Like, if in using Git you never branched but only used `master` for everything: that's a blockchain.

OK, but are there any transactions on that? What’s the daily volume?

TPS has slowed to a crawl recently but had been much higher. See for yourself. https://thetangle.org/live