My first question about this was: USDT on which chain? As you may recall, USDT made the genius move (as far as their balance sheet was concerned) early on to be chain agnostic -- seems like now they have USDT on every chain imaginable.

So which chain are they using when you swap BTC to USDT? As far as I can tell, the answer ethereum, but also like...all the chains?

With this launch, Boltz natively supports atomic swaps between Lightning and tBTC on Arbitrum. tBTC is Threshold’s ERC20 wrapper for Bitcoin. Similar to WBTC, but open to mint, unmint and use for anyone. By adding a DEX Swap hop between tBTC and USDT0 on Arbitrum, a form of atomic swap that is designed to handle assets of different denominations, Boltz can offer Lightning ↔ USDT swaps.

Here's a diagram:

Seems like it goes lightning -> tBTC on arbitrum (which is on ethereum) -> uniswap -> USDT0 -> USDT on any chain you like.

For Boltz, this is a game-changer. By concentrating liquidity on Arbitrum and leveraging the OFT protocol, we can efficiently serve users across every USDT0-connected network while maintaining our liquidity and integration efforts focused - in one place. You can find the full list of supported networks, along with contract addresses, here and here.

I remember hearing about Tether's USDT0 before, but not being clear about what it was.

So now we have to ask: What the hell is USDT0? That may be a separate post.

There is no doubt that this is a bunch of shitcoin stuff: even if you hold USDT "self-custodially" it seems to me that Tether has the ability to freeze your coins which is the the same thing as saying USDT can only be held in custody.

So, if you are swapping to USDT, you are already far into shitcoin-land.

But I am also convinced that one of the main reasons bitcoin adoption is sluggish is that people can't spend it anywhere. Boltz seems to think that these swaps will make it much easier to spend sats at places that don't take sats:

Here are some of the use cases this unlocks:

• Top up your favorite crypto debit card with Lightning. Most support USDT natively, yet Lightning is nowhere to be found. With Boltz you can now swap Lightning into USDT and load your card in seconds.
• Send Lightning straight into your bank account. Move from Lightning directly into USD in your FV Bank, Revolut, or Xapo account. The entire flow from sats to spendable fiat stays non-custodial until your Bank credits the USD.
• Hedge volatility on your terms. Markets dipping? Swap Lightning into USDT and hold USD-stable value without surrendering control to anyone. When you’re ready to stack sats again, swap back just as easily.
• Accept Lightning, settle in USDT. A coffee shop running a Lightning POS can sweep daily revenue into USDT or even directly split the settlement between USDT and Bitcoin with the upcoming integration of USDT swaps in our popular Boltz BTCPay Plugin.

What is the difference between this swap thingie from boltz and Square "turning on" lightning payments for all Square terminals?What is the difference between this swap thingie from boltz and Square "turning on" lightning payments for all Square terminals?