The Lightning Network is a Layer-2 protocol, originally proposed by Joseph Poon and Thaddeus Dryja, that moves Bitcoin transactions off the main blockchain into bidirectional payment channels, allowing near-instant transfers without recording every single payment on the base layer. It was designed specifically to solve Bitcoin's low base-layer transaction throughput.
Why Bitcoin's base layer needed help
Bitcoin's original 1 MB block size, expanded to roughly 2 MB of effective capacity after SegWit, combined with a 10-minute average block time, limits Layer-1 to only about 7 transactions per second globally. Recording something as small and frequent as a cup of coffee purchase directly on that ledger would make the blockchain's storage requirements grow at an unsustainable rate. The Lightning Network addresses this by keeping high-frequency, low-value transactions off the base chain entirely.
Paying someone without a direct channel
A user does not need to open a dedicated channel with every merchant or counterparty they want to pay. Hashed Timelock Contracts (HTLCs) allow a payment to route across a chain of existing connected channels instead. If Alice wants to pay Carol and only Bob has channels open with both of them, the payment can route through Bob cryptographically: either the full payment goes through and Carol receives it, or the timelock built into the contract expires and Alice's funds are automatically returned, with no scenario where funds get stuck in between.
What running a channel actually requires
Lightning's design shifts some responsibility onto the participants themselves. Watchtower nodes exist specifically to monitor the blockchain on a user's behalf and catch an offline channel partner attempting to broadcast an outdated, more favorable channel state while the honest party isn't watching. Beyond security, running a useful node also requires active liquidity management, since a channel needs a workable balance of inbound and outbound capacity to reliably route payments in both directions rather than only one.
- Watchtower nodes monitor the blockchain to prevent an offline channel partner from broadcasting an outdated channel state.
- Channel liquidity management requires balanced inbound and outbound capacity for reliable routing.