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Lesson 19 / 21 · Advanced

Lightning liquidity has direction

Capacity is not the same as the ability to receive.

14 MIN WITH PRACTICEREAD → TRY → REFLECTNO WALLET NEEDED

By the end, you’ll be able to…

  • Distinguish inbound and outbound capacity conceptually.
  • Explain why a route may fail despite visible channels.
Your learning map

Three questions to carry into this lesson.

01Distinguish inbound and outbound capacity conceptually.
02Explain why a route may fail despite visible channels.
Use these goals to guide your reading. Try the paper exercise, then explain the result in your own words.

Balances determine direction

A channel’s total capacity describes value committed to it, but the distribution of balances affects what can move in each direction. A node can have channels and still lack sufficient ability to receive a particular payment. Looking only at the capacity headline omits the practical direction of available liquidity.

A route is a set of constraints

The sender needs a usable path through channels whose participants are available and able to forward the amount. Public topology does not reveal every current balance or operational condition. Attempts can fail and alternative routes may be tried. Small successful payments therefore do not prove that an arbitrary larger payment will work at the same time.

Treat liquidity services as services

An operator may consider channels, liquidity providers or other arrangements, each with fees and assumptions. This lesson does not recommend a provider or ask for a channel opening. A comparison should describe costs, custody, uptime expectations, limits and recovery behavior. For a community checkout, communicate a failed attempt honestly and offer a verified alternative without pressuring the buyer to accept unfamiliar infrastructure.

Your turn / A paper experiment

Practice on paper

A fictional node has a channel of 100,000 sats, with almost all spendable balance on its own side. Why might an incoming 60,000-sat payment still fail?

I’ve tried it — show the worked answer

Total capacity does not establish inbound liquidity. The remote side and the rest of the route must be able to carry the incoming payment, subject to channel constraints and current availability.

Want to explore with buttons and instant feedback? Try the practice lab ↗

Think it through

Make a choice. Discover why.

Choose an answer and check the explanation. You can retry as often as you like. These are practice questions, not a test of mastery; answers are not saved or sent.

1. Does large total channel capacity guarantee any incoming payment succeeds?
  • Yes
  • No
Read the explanation

No. Direction and route conditions matter.

2. Does one successful small payment prove unlimited capacity?
  • Yes
  • No
Read the explanation

No. Amount and timing change the constraints.

One idea to take with you

Measure the direction and usable route, not only total capacity.

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