A layer 1 or L1 blockchain is the basic network of a blockchain ecosystem. It operates independently – without relying on other chains for validation or execution – and handles everything from transaction processing to consensus and data storage on its own ledger.
A layer 1 blockchain, often called the mainnet or settlement layer, is the ground floor on which all other blockchain layers, including sidechains and layer 2s, are built.
Where Layer-2s extend performance on top of existing networks, Layer-1s stand alone. They define their own rules, run their own validators, and issue their own native tokens. Bitcoin, Ethereum, Solana, Cardano and Avalanche all fit this description.
In this article we will look at the history and features of Web3’s foundational layer.
Within a layer-1: how it is constructed
Every L1 blockchain contains several core components that make it both functional and secure:
- Network nodes: Thousands of independent computers maintain identical copies of the blockchain and broadcast data to each other. Their distributed nature prevents censorship and single points of failure.
- Consensus layer: The rulebook for agreement. It determines how participants decide which transactions are valid and how blocks are added to the chain.
- Execution layer: On programmable blockchains like Ethereum or Solana, this layer runs smart contracts: self-executing code that powers decentralized apps and automated transactions.
- Native cryptocurrency: Each L1 has its own coin that pays transaction fees, rewards validators, and supports on-chain governance. BTC secures Bitcoin, ETH powers Ethereum, and ADA powers Cardano.
How layer 1s process transactions
Within different networks the flow is largely the same:
- Validation: Transactions are checked to ensure they comply with protocol rules and have the correct signatures and balances.
- Blocking: Verified transactions are bundled into candidate blocks.
- Agreement: Nodes agree on which block to add next, using the algorithm chosen by the network.
- Finality: Once confirmed, the block becomes immutable; Balances and contract details are updated via the network.
This cycle repeats itself continuously, thousands of times a day, without central supervision.
Consensus mechanisms: the heart of the blockchain
The consensus mechanism defines how a blockchain reaches agreement and shapes its speed, security and energy profile. Although there are many different consensus mechanisms, the most important are:
- Proof of work (PoW)– Introduced by Bitcoin, PoW miners solve cryptographic puzzles through computation. It is extremely secure, but energy intensive and limited to approximately seven transactions per second (TPS).
- Proof of stake (PoS)– Validators lock tokens as collateral to earn the right to validate blocks. It replaces energy consumption with economic incentives.
- Delegated proof of stake (DPoS)–Used by Binance Smart Chain and others, this model relies on a smaller, chosen set of validators to increase efficiency, trading off some decentralization for speed.
- Evidence of history (PoH)–Solana’s unique system timestamps transactions before consensus, enabling thousands of TPS and sub-second block times.
The leading layer-1 blockchains
Bitcoin (BTC) – Proof of Work: the first and most secure blockchain. Processes approximately 7 TPS using energy-intensive mining, emphasizing decentralization and immutability over speed.
Ethereum (ETH) – Proof of Stake: the largest programmable blockchain, supporting smart contracts, NFTs and DeFi. After The Merge in 2022, it reduced energy consumption by more than 99% while laying the foundation for scalability through rollups and upcoming sharding.
Solana (SOL) – Proof of History + PoS: Known for high throughput and low fees, Solana timestamps transactions before consensus to achieve sub-second block times.
Cardano (ADA) – Ouroboros Proof of Stake: a research-driven blockchain that emphasizes formal verification and layered architecture to separate settlement and computation.
Avalanche (AVAX) – Avalanche Consensus: uses probabilistic sampling to quickly reach consensus. Provides sub-second finality and supports customizable subnets for app-specific chains.
Binance smart chain (BNB) – Delegated proof of stake: Operated by a limited validator set, BSC trades decentralization for performance and offers fast, low-cost transactions compatible with Ethereum’s tools.
Timeline: major milestones at layer 1
- January 2009: Bitcoin is launched proving decentralized consensus via Proof of Work as the first fully functional blockchain.
- July 2015: Ethereum goes live, introducing programmable, Turing-complete smart contracts to the blockchain ecosystem.
- September 2017: Cardano launches its Byron mainnet, formalizes Proof of Stake with the Ouroboros protocol and creates a layered architecture.
- September 2020: Avalanche launches its mainnet and introduces a fast consensus mechanism and a subnet framework for customizable chains.
- September 2022: Ethereum completes The Merge, moving from Proof of Work to Proof of Stake and reducing energy consumption by more than 99%.
- October 2023: Celestia is launching as the first modular blockchain focused on data availability and consensus separation.
- August 2025: Circle unveils Arc, a stablecoin-focused layer 1, with a public testnet live in October and a mainnet planned for 2026.
Every blockchain aims to address the same underlying challenge: the blockchain trilemma.
The blockchain trilemma
Ethereum co-founder Vitalik Buterin coined the term “blockchain trilemma” in 2017 to describe the challenge that blockchains cannot simultaneously maximize decentralization, scalability, and security, forcing tradeoffs between the three.
- Security – Protection against manipulation or attack.
- Scalability – Ability to process large volumes efficiently.
- Decentralization – Distribution of control over many independent nodes.
Scaling layer-1s
Developers are constantly looking for ways to increase blockchain throughput without compromising decentralization – a direct response to the blockchain trilemma.
- Shards: This technique splits the network into smaller parts, or shards, that process data in parallel to lighten the workload of nodes and increase capacity. Ethereum originally planned for 64 shards, but in late 2025 shifted its focus to proto-danksharding and dansharding: upgrades focused on data availability for layer-2 combinations rather than full on-chain execution. Proto-dankharding (EIP-4844) introduces data blobs to improve storage efficiency, while full dansharding is still in development.
- Consensus Optimization: Moving from energy-intensive Proof of Work to Proof of Stake – such as Ethereum’s 2022 Merge – dramatically improves efficiency. Some newer networks combine or adapt consensus models to balance speed, cost and security.
- Block parameters: Larger blocks and shorter intervals can increase throughput but risk centralization. Larger blocks require more bandwidth and storage; faster blocks cause synchronization problems and the number of orphaned blocks.
- Protocol upgrades: Bitcoin’s 2017 Segregated Witness (SegWit) is a classic example of direct layer-1 scaling. By separating signature data (“witnesses”) from transaction data, SegWit freed up block space and enabled more transactions per block without expanding its size.
Real world applications
Layer-1 blockchains powered DeFi and powered lending, exchanges, and stablecoins through smart contracts. Ethereum and Solana enabled NFTs and gaming, bringing digital property on-chain. They also improved supply chain transparency, secured digital identity, and enabled tokenization of real-world assets such as property and art.
Why they still matter
Layer 2s and sidechains help with speed, but layer 1s remain the source of the truth. They provide a final settlement, an unchanging history, and shared trust for all that is built above it.
Blockchain technology has advanced far beyond its origins in 2009, and the work has not slowed down. In November, the Ethereum Foundation announced its next big step: the Ethereum Interoperability Layer, which will allow any Ethereum L2 to communicate instantly with any other L2.
As blockchain technology evolves – from energy-intensive mining to modular, quantum-resistant architectures – layer 1 blockchains continue to define the infrastructure of the decentralized internet.