If you have used Base for a while, you have probably seen the terms "layer 2" and "layer 3" in the same sentence. Base is a layer 2 network. Some projects go one step further and launch their own chain on top of a layer 2. Those are usually called layer 3 chains, or L3s, and many of them are also described as appchains.
This article explains what an L3 is, why teams build one, and what changes for you as a wallet owner when your funds move to a chain that sits above Base. It is educational, not a recommendation to use any specific chain.
The layers in plain terms
- Layer 1 (L1): Ethereum. This is the base layer that provides final security and settlement.
- Layer 2 (L2): Networks like Base. They run transactions off Ethereum's main chain, then post data and proofs back to Ethereum. That is how fees stay low while security is inherited from Ethereum. If you want the background, see how Base stays secure.
- Layer 3 (L3): A chain that uses an L2 as its settlement layer, the same way an L2 uses Ethereum. An L3 posts its data and state to the L2, and the L2 in turn posts to Ethereum.
So an L3 is the same rollup idea applied one level higher. The word "layer" describes where a chain settles, not how good or fast it is.
What an appchain is
An appchain is a blockchain built mainly for one application or community, such as a game or a social network. It can be an L1, L2, or L3. An L3 appchain on Base runs its own chain for its own users and settles to Base.
Why teams build an L3
Teams usually give reasons like these:
- Cheaper, more predictable fees. A busy app can be affected by unrelated activity on a shared network. On its own chain, the app controls its own block space.
- Custom rules. The team can choose its own gas token or block time.
- Easy connection to Base. Because it settles to Base, moving value between Base and the L3 can be simpler than bridging from an unrelated network.
One well known example is Degen Chain, which launched in 2024 as an L3 built with the Arbitrum Orbit stack that settles on Base. It uses the DEGEN token as its gas token. It shows that an L3 can differ a lot from Base: different technology, gas token, and operators. If you look at a specific L3, check its current status and documentation yourself, because chains change over time.
What is different for you as a user
Moving to an L3 is not the same as moving between two apps on Base. Several things change.
1. Your address may be the same, but the network is not
Your address will usually look identical on an L3, but the L3 has its own chain ID, RPC endpoint, and balances. See what a chain ID is and what an RPC endpoint is for why this matters. Sending tokens on the wrong network is a common cause of lost funds, covered in what happens if you send tokens to the wrong network.
2. You need the L3's gas token
Base uses ETH for gas, but many L3s use a different token. If you bridge in without the gas token, you may be unable to transact on the L3. Check what the chain uses before you bridge a large amount.
3. You depend on more parties
Every extra layer adds parties you rely on: the operator who sequences transactions, the data availability arrangement, and the bridge contracts that connect the L3 to Base. Some L3s use a separate data availability layer to keep costs down, which lowers fees but changes what you are trusting. Ask what happens if the operator goes offline, and whether you can still withdraw without their cooperation.
4. Withdrawals can take longer
Getting funds out of an L3 back to Base follows the L3's own rules. Getting funds all the way out to Ethereum means passing through the L2 as well, so the delays can add up. The exact timing depends on the design of each chain, so read its documentation before assuming a withdrawal will be quick. You can compare this with withdrawing from Base to Ethereum.
5. Liquidity may be thinner
Smaller chains often have fewer tokens and less liquidity, so a swap can move the price more. Pay extra attention to price impact.
Bridging to an L3 safely
Bridges are a common place for users to lose money, so a few habits help:
- Use the official bridge link from the project's own site, and confirm the URL yourself instead of trusting a link sent in a message.
- Start with a small test amount and confirm it arrives before moving more.
- Check the destination network and the gas token before you confirm.
- Keep a small amount of the gas token so you can always make a transaction on the L3.
- Review the approvals you give to any contract on the new chain. See how to check and revoke token approvals.
For more on the risks, read why bridging carries different risks than swapping.
How to think about the tradeoffs
There is no single answer to whether an L3 is good or bad. It is a design choice with tradeoffs:
- Benefits: lower and more predictable fees for a specific app, more control for builders, and a shorter path to Base compared with an unrelated chain.
- Costs and risks: more layers to trust, possible operator control, potentially slower exits, thinner liquidity, and more room for mistakes when moving funds between networks.
A cautious approach for beginners is to move only what you need to an L3 for a specific purpose. Nothing here is financial advice, and a chain being new or cheap says nothing about whether an app on it is safe.
Where Simple Base Swap fits
Simple Base Swap is built for one network on purpose: Base. That means fewer chain switches, fewer bridges, and fewer places to make a costly mistake. If you explore an L3, do it deliberately and understand how funds get in and out first.
Key takeaways
- An L3 settles on a layer 2 such as Base instead of directly on Ethereum.
- L3s can offer lower fees and custom rules, but they add layers of trust, and withdrawals can be slower.
- Your address may look the same, but the chain, gas token, and balances are separate.
- Bridge carefully: official links, small test amounts, and a check of the destination network.