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How do layer 2 networks work?
Sending a payment on Ethereum's main chain can cost dollars at a busy moment. The same payment on a layer 2 can cost cents.
The trick is batching. Thousands of transactions are run elsewhere and posted back to Ethereum as one compressed record, so they share a single fee.
Why it's cheaper
A layer 2 runs transactions off the main chain and posts them back in batches, so the main chain's fee is split among many users.
Busy blockchains can get slow and expensive, because every transaction competes for limited space in each block. Layer 2 networks move most of the work elsewhere.
The most common type is a rollup. It bundles many transactions together and posts a compressed record to the main chain, so they inherit much of its security while each user pays a fraction of the fee. Arbitrum, Optimism and Base are examples on Ethereum.
The trade-offs are real. Moving money between layers uses bridges, some rollups make withdrawals back to the main chain wait about a week, and many are still run by a single company that orders the transactions.
Two kinds of rollup
Optimistic rollups, like Arbitrum, Optimism and Base, assume batches are honest and allow a challenge window, usually about a week, for anyone to prove fraud.
Zero-knowledge rollups attach a mathematical proof to each batch, so the main chain can verify it straight away. They allow faster withdrawals but are more complex to build.
What to check before using one
Look at how long withdrawals take, who runs the sequencer, and whether the team can upgrade the contracts without delay. Independent trackers rate rollups on these points.
For everyday use, fees on a major rollup are often cents, compared with dollars on Ethereum's main chain at busy times.
The fee math of batching
One $30 batch shared by 3,000 users costs each of them a cent. Add a small execution charge and the fee is about 1.4 cents.
A rollup user's fee has two parts. One is a small charge for running the transaction on the layer 2, and the other is a share of the cost of posting the batch to Ethereum. The second part is where batching pays off. Take an example where posting one batch to Ethereum costs $30 and the batch holds 3,000 transactions. Each user's share is one cent. Add an example layer 2 execution charge of $0.004 and the total is about $0.014.
Compare that with sending the same transaction directly on Ethereum at a busy moment, which might cost a few dollars. The difference comes from splitting one expensive record among thousands of users, and from compressing the data so the record itself is small.
Fees fell sharply after Ethereum's Dencun upgrade on March 13, 2024. It added a cheaper type of data space, called blobs, designed for rollups to post their batches. Many rollups passed the savings on, and typical fees on major layer 2s dropped to fractions of a cent. The catch is that the batch cost still rises when Ethereum is busy, and a quiet rollup with few users per batch spreads the cost over fewer people, so fees can vary from one network to another.
Training wheels: how rollups are graded
Rollups range from team-controlled to run by code. Checking a rollup's stage shows how much you rely on its operators rather than on Ethereum.
Most rollups launched with what developers call training wheels, meaning a team or small committee that can upgrade the contracts, pause the system or step in if something breaks. That's useful while the code is new, but it means users trust that group, not only Ethereum.
L2BEAT, an independent tracker, sorts rollups into stages. Stage 0 rollups rely heavily on their operators, and a bug or a bad actor among them could put funds at risk. Stage 1 rollups have a working proof system so anyone can challenge or verify batches, but a security council can still override it in an emergency. Stage 2 rollups are run fully by code, with any upgrade giving users enough time to withdraw first if they disagree.
You can check any rollup on L2BEAT in a minute. Look at its stage, the length of its withdrawal delay, who can upgrade it and whether users can exit on their own if the operator stops posting batches. Many large rollups have moved from Stage 0 to Stage 1, and the stage can change, so look again before moving large amounts.
Key terms
Layer 1
A base blockchain that settles its own transactions.
Rollup
A layer 2 that posts compressed batches to its layer 1.
Bridge
A way to move assets between chains.
Sequencer
The operator that orders transactions on a rollup.
Cheaper fees come with other trade-offs
Who runs it. Many layer 2s still rely on one company to order transactions.
How fast you can leave. Some withdrawals back to the main chain take about a week.
What the token does. On many layer 2s fees are paid in ether, so usage doesn't automatically help the token.
What people get wrong
A layer 2 token isn't always needed to use the network. On many rollups, fees are paid in ether.
Layer 2s aren't separate copies of Ethereum. They depend on the main chain to settle their records.
Why it matters
A lot of everyday crypto activity now happens on layer 2s, and their tokens make up a whole sector on KryptoKap.
Common questions
Is Solana a layer 2?
No. Solana is its own layer 1, designed to handle many transactions directly on the main chain.
Why do withdrawals from some layer 2s take a week?
Optimistic rollups leave time for anyone to challenge a fraudulent record before funds are released to the main chain. Third-party bridges can be faster, for a fee and extra risk.
Why do layer 2 fees go up sometimes?
The fee includes a share of the cost of posting data to Ethereum, so it rises when Ethereum is busy. Heavy demand on the layer 2 itself, such as a popular token launch, can also push up its own execution fee, the same way demand pushes up fees on any chain.
