What is a millisatoshi? I thought satoshi is the smallest unit?

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1

I encountered 'millisatoshi' (msat) while browsing Lightning Network..., see screenshoot below:

Taken from https://lnmainnet.gaben.win/

And subsequently I found it mentioned here:

https://github.com/ElementsProject/lightning/blob/master/README.md#sending-and-receiving-payments

Obviously, I am curious... I thought satoshi is the smallest unit?

Rosdi Kasim

Posted 2018-01-28T10:02:13.633

Reputation: 185

It must be a mistake. I have nothing concrete from your reference to back up my opinion, hence not an answer, but they can not possibly mean millisatoshi, it is smaller than the divisible one satoshi unit of Bitcoin.Willtech 2018-01-28T10:54:45.513

But, I will try and find out definitively.Willtech 2018-01-28T11:01:58.633

@Willtech I added screenshot for further clarification.Rosdi Kasim 2018-01-28T11:20:59.087

Seems @MeshCollider has your answer.Willtech 2018-01-29T11:13:24.457

Answers

10

It's not a mistake, it's literally a thousandth of a satoshi. A satoshi is the smallest unit for bitcoin, but lightning can transact with even smaller units while channels are open. The amount is rounded down to the nearest satoshi when the channel is closed and broadcast to the blockchain to adhere to bitcoins limit.

MeshCollider

Posted 2018-01-28T10:02:13.633

Reputation: 8 735

So, a LN transaction for 50msat would be broadcast to the blockchain as what amount?Willtech 2018-01-28T11:20:59.647

It would not be, its less than 1 satoshi so if your balance was that small at closing time you would get 0.MeshCollider 2018-01-28T11:29:11.687

I suppose that's fine, you are technically not losing any BTC since you didn't even have 1sat.Willtech 2018-01-28T11:35:40.743

"The amount is rounded down to the nearest satoshi", so... even 999 msat would be rounded down to 0 sat. Which is technically fair and easier to implement.Rosdi Kasim 2018-01-28T14:34:35.250

I thought they wanted to use probabilistic payments. Are you sure about the rounding down?Murch 2018-01-28T14:44:26.990