People use at least three different meanings of “Bitcoin Layer 2”:
1⃣Network L2: an interoperable protocol cryptographically pegged to Bitcoin in a trustless manner. It preserves Bitcoin’s peer-to-peer nature and disintermediated verifiability, and does not use IOUs.¹
2⃣Broader technical L2: a protocol that extends Bitcoin’s functionality. Bitcoin is locked on L1 and represented or used on L2. This can involve additional trust in centralized actors or network operators, with eventual settlement back to Bitcoin.²
Übersetzen mit DeepL 3⃣Monetary L2: any off-chain interaction that transfers a BTC balance from one entity to another, whether as an IOU or as actual ownership.¹
When I say “Bitcoin L2”, I mean definition #1.
Under that definition, I do not consider Liquid, Cashu, Fedimint, or Spark to be Bitcoin Layer 2s.
They can still be useful technologies built around Bitcoin. I just would not call them Bitcoin L2s.
¹ The Semantics of the Bitcoin Layers, Bitcoin Magazine bitcoinmagazine.com/culture/the-semantics-of-the-bitcoin-layers
² Bitcoin’s Layered Design: The Key to Greater Utility, Blockstream blog.blockstream.com/bitcoins-layered-design-the-key-to-greater-utility/