How do assets live near Bitcoin?
RGB does this with client-side validated contracts. Spark does it with token support inside its fast transfer system. Both are trying to make dollars and other assets feel native to Bitcoin wallets.
Source-checked May 13, 2026
Bitcoin L2s, explained by what they do
RGB, Arkade, Lightning, and Spark all try to make Bitcoin useful beyond slow layer-1 payments. They do it with very different tradeoffs: channels, client-side validation, virtual UTXOs, statechains, operators, and exits.
Start here
The four questions most people actually ask
Before the protocol details, use these cards to sort the landscape: assets, swaps, payments, and app-style execution.
What is best for paying someone?
Lightning is the mature BTC payment network. Spark tries to make transfers feel simpler by avoiding channel management. Arkade aims at fast VTXO-based payment and app flows.
Why are swaps such a big deal?
Assets need markets. RGB swaps help users move between sats and RGB assets. Spark already has Flashnet-style AMM infrastructure for token swaps and liquidity pools.
Where do richer Bitcoin apps fit?
Arkade is the most directly app-oriented design here. RGB gives typed asset contracts, Spark gives fast token transfer rails, and Lightning stays focused on routed BTC payments.
Choose a protocol
What each Bitcoin L2 moves off-chain
Each protocol moves routine activity off the base chain, then preserves some way to settle, anchor, or escape back to Bitcoin.
Lightning simulator
Why a Lightning payment can fail even when a path exists
Lightning wallets route through channels. The graph can find a path, but the hidden balance direction can still make payments fail and retry. Each channel also sets its own forwarding fee, so wallets usually try to balance price and reliability instead of blindly taking the shortest path.
Ready: the wallet will choose the cheapest viable path it knows.
Fee labels are per channel. Lower ppm means cheaper forwarding for that hop.
Swap lab
Why swaps are the first real app for new Bitcoin assets
Issuing an asset is only step one. RGB needs markets for its client-validated assets, while Spark already has Flashnet-style swap infrastructure for AMMs, liquidity pools, and fast token trading.
Settlement sketch
both legs settle or neither does
Ready: check the quote, lock both sides, then settle together.
Native USDT
Why does every chain want native USDT?
Native USDT brings a familiar dollar asset directly to the network where users already hold funds. That gives wallets, exchanges, market makers, merchants, and apps a shared unit of account without forcing every user through a wrapped asset, a bridge, or a custodial exchange.
Fit matrix
Red, yellow, green tradeoff map
Start with the thing you care about. Green means the design naturally fits, yellow means it can work with tradeoffs, and red means there is real friction.
Good fit
Workable
Friction
Tap any protocol chip
You will get the plain-English reason for that score, including what a beginner should remember before building or using it.
| Protocol | Best mental model | Strong at | Watch out for |
|---|
Checkpoint
Can you explain the differences?
Short questions, practical answers. The goal is to leave with a usable mental model, not protocol maximalism.
Glossary
Terms that unlock the whole map
Sources
Primary references used by network
Each group points to the docs or announcements used for that part of the lesson, so you can follow the simplified explanation back to the source.