Key Takeaways
The blockchain trilemma explains why most networks struggle to achieve security, decentralization, and scalability at the same time.
Layer 1 scaling solutions change the base blockchain directly, such as upgrading the consensus mechanism or adding sharding.
Layer 2 solutions build on top of a Layer 1 to handle more transactions off the main chain, reducing congestion and fees.
Most blockchain ecosystems are moving toward a combination of Layer 1 improvements for long-term security and Layer 2 networks for everyday speed and affordability.
Introduction
Blockchain networks are becoming more popular, and with more users come more transactions. While the technology offers real utility, handling large-scale demand remains a significant challenge. Public blockchains that prioritize decentralization and security often struggle to process transactions quickly and cheaply.
This tension is known as the blockchain trilemma: it is difficult for a decentralized network to be secure, decentralized, and scalable all at once. Most networks prioritize two of these properties, which can limit the third.
Developers have created two broad approaches to address this. Some solutions modify the core blockchain (Layer 1), while others build additional networks on top of it (Layer 2). Both approaches have trade-offs, and many ecosystems now use a combination of both.
Layer 1 vs. Layer 2
The term Layer 1 blockchain refers to the foundational blockchain where transactions are finalized. Examples include Bitcoin, Ethereum, BNB Chain, and Solana. These are the base networks that other protocols can build on.
Layer 2 refers to protocols built on top of a Layer 1. They process transactions off the main chain and then report the results back. Examples include the Lightning Network (for Bitcoin) and Arbitrum, Base and zkSync (for Ethereum).
The key distinction is where the work happens. Layer 1 solutions change the rules of the base network itself. Layer 2 solutions create a separate environment to handle more activity, then settle back to Layer 1 for security.
Common Layer 1 Scaling Solutions
Consensus mechanism upgrades
Some blockchains have switched from energy-intensive systems like proof-of-work (PoW) to more efficient ones like proof-of-stake (PoS). Ethereum completed this transition in September 2022 with "The Merge". PoS selects validators based on staked funds rather than computational work, which can improve transaction throughput and energy usage.
Sharding
Sharding divides the blockchain into smaller partitions called shards. Instead of every node processing every transaction, the work is spread across multiple groups. This allows the network to handle more transactions in parallel, potentially increasing overall capacity.
Ethereum's longer-term roadmap includes full sharding through a feature called Danksharding, though this remains in development. A preliminary step, EIP-4844 (blob transactions), was introduced in March 2024 and significantly reduced data costs for Layer 2 networks.
Block size increases
A simpler approach is to increase the maximum size of each block, allowing more transactions to be included per block. This can raise throughput without major protocol changes. However, larger blocks require more storage and processing power, which may make it harder for regular computers to participate as network validators, potentially affecting decentralization.
Common Layer 2 Scaling Solutions
Rollups
Rollups bundle many off-chain transactions together and submit a compressed summary to the main chain. This reduces the data each transaction adds to Layer 1, lowering fees and increasing throughput. Rollups have become the primary scaling method for Ethereum.
There are two main types. Optimistic rollups (used by Arbitrum and Base) assume transactions are valid by default and allow a challenge period for disputes. ZK rollups (used by zkSync and Scroll) generate cryptographic proofs that confirm transaction validity immediately, without a waiting period.
State channels
A state channel lets two parties transact directly off-chain as many times as they need. Only the opening and closing balances are recorded on the blockchain. This works well for repeated interactions between the same parties, such as micropayments or gaming.
The Bitcoin Layer 2 networks section covers the Lightning Network, which uses state channels to enable fast, low-fee Bitcoin payments between participants.
Sidechains
Sidechains are independent blockchains that run alongside a Layer 1 and have their own validators and consensus rules. They connect to the main chain via a bridge. Polygon PoS is a well-known example. Sidechains can be faster and cheaper but are responsible for their own security, unlike rollups which inherit security from the underlying Layer 1.
Nested blockchains
In a nested blockchain setup, the main chain delegates work to secondary chains. These child chains handle transactions and return the results to the parent chain. The Plasma framework is an early example of this approach for Ethereum, though it has largely been superseded by rollups in practice.
Layer 1 vs. Layer 2: Key Differences
Both layers aim to improve network performance, but they approach the problem differently. Here is a summary of the main differences:
Purpose: Layer 1 is the base source of truth and settlement layer. Layer 2 is built to increase throughput and reduce fees for that base layer.
Method: Layer 1 changes the protocol rules directly. Layer 2 offloads processing to a secondary network or application.
Security: Layer 1 relies on its own decentralized consensus. Layer 2 networks typically rely on Layer 1 for final security and data availability.
Complexity: Layer 1 upgrades require network-wide consensus and can be disruptive. Layer 2 networks can often be deployed or updated without changing the base chain.
Limitations of Scaling Solutions
Neither approach is without trade-offs.
Layer 1 upgrades can be slow and politically complex. Major protocol changes, such as sharding or consensus overhauls, require broad agreement among validators, developers, and stakeholders. Hard forks, when the community cannot agree, can split the network.
Layer 2 networks add friction for users. Moving funds between a Layer 1 and a Layer 2 requires bridging, which can take time and introduce security risks. Liquidity is often fragmented across different L2 networks, and some rely on centralized sequencers to order transactions, which may introduce a central point of trust.
FAQ
What is the difference between Layer 1 and Layer 2?
Layer 1 is the base blockchain where transactions are finalized, such as Ethereum or Bitcoin. Layer 2 is a secondary network built on top of a Layer 1 to handle more activity off-chain before settling back to the main chain. Layer 1 handles security and settlement; Layer 2 handles speed and cost.
Are Layer 2 networks as secure as Layer 1?
It depends on the type of Layer 2. Rollups inherit much of their security from the underlying Layer 1, since transaction data is submitted to the main chain. Sidechains, however, maintain their own validator sets and do not directly inherit Layer 1 security. Users should understand how a specific L2 handles security before using it.
Why do rollups have lower fees than Ethereum?
Rollups bundle many transactions together and submit a compressed batch to Ethereum. This means the cost of one Ethereum transaction is shared across many rollup transactions, reducing the per-transaction fee significantly. The Ethereum Dencun upgrade in March 2024 reduced these data costs further using blob transactions.
What is the blockchain trilemma?
The blockchain trilemma refers to the difficulty of achieving security, decentralization, and scalability simultaneously. Most blockchain designs prioritize two of these properties, which constrains the third. Scaling solutions, whether at Layer 1 or Layer 2, are largely attempts to address this constraint.
Which Layer 2 networks are the most widely used?
As of today, Arbitrum, Base and zkSync are among the most active Ethereum Layer 2 networks by transaction count and total value locked. For Bitcoin, the Lightning Network remains the primary Layer 2 for payments. Adoption continues to grow as more applications and users move to L2 networks for lower costs.
Closing Thoughts
Scaling is one of the most active areas of blockchain development. Layer 1 improvements like sharding provide long-term capacity growth, while Layer 2 networks offer practical speed and cost benefits today. Most major blockchain ecosystems are moving toward a layered architecture, combining a secure and decentralized base chain with faster and cheaper networks built on top.
Further Reading
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