How to bridge from Layer 1 blockchains to Layer 2 blockchains

Understanding the architecture of blockchain technology is essential for grasping how digital assets and information traverse the diverse landscape of distributed ledgers.

At their core, blockchain layers are foundational elements that categorize the functionalities and scalability solutions within the network.

Layer 1 blockchains, also known as the base layer, are the underlying protocols of decentralized networks. These include prominent blockchains like Bitcoin and Ethereum — responsible for the network's security and consensus mechanisms.

Layer 2 solutions were conceptualized to address the limitations in scalability and transaction throughput that Layer 1 blockchains face. Operating atop the base layer, these solutions aim to enhance the network's capacity without compromising its security or decentralization.

Layer 2 solutions come in various forms, including state channels, side chains and rollups — each offering different mechanisms to alleviate congestion on the main blockchain. These solutions facilitate quicker transactions and lower fees by handling transactions off the main chain, thereby increasing the overall throughput.

As blockchain technology evolves, the interplay between Layer 1 and Layer 2 becomes increasingly significant, especially when considering the user experience and the network's ability to handle growing demand. With the rise of decentralized finance and non-fungible tokens, the need for robust Layer 2 solutions is more pronounced than ever — highlighting the importance of understanding these blockchain layers for users and developers alike.

Layer 1 blockchains explained

Layer 1 blockchains, often referred to as the foundational infrastructure of the cryptocurrency ecosystem, are the original networks upon which digital currencies and applications are built. These primary blockchains — such as Bitcoin, Ethereum and Solana — are designed to maintain the ledger's security and facilitate consensus amongst their participants.

The consensus mechanism, a core feature of Layer 1, is the process by which the network agrees on the state of the blockchain, ensuring the integrity and immutability of the transaction data. For instance, Bitcoin employs a proof-of-work mechanism, which requires computational work to validate transactions and create new blocks, while Ethereum transitioned to a proof-of-stake system, where validators are chosen to create new blocks based on the number of coins they hold and are willing to "stake" as collateral.

Despite their pivotal role in the blockchain ecosystem, Layer 1 networks have challenges, particularly regarding scalability. As the user base and transaction volume have grown, these networks have encountered bottlenecks, leading to slower transaction times and higher fees. This has spurred the development of various scaling solutions that aim to enhance the networks' capacity.

Some Layer 1 scaling strategies include increasing block sizes to accommodate more transactions, sharding to process transactions in parallel, and updating consensus mechanisms for greater efficiency. These innovations are crucial for the continued growth and adoption of blockchain technology, as they directly address the trade-offs between decentralization, security, and scalability inherent in these foundational networks.

Introduction to Layer 2 blockchains


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Layer 2 blockchains are a vital innovation designed to address the inherent limitations of Layer 1 blockchains — particularly scalability and transaction speed — which become increasingly pressing as the network grows in popularity. These secondary layers operate on top of the foundational Layer 1 blockchains, like Ethereum, and offer various scaling solutions to facilitate faster and more cost-effective transactions. By leveraging the security and decentralized nature of the underlying primary blockchain, Layer 2 solutions maintain the trust and integrity that are core to blockchain technology while enhancing performance.

Among the diverse array of Layer 2 solutions, some notable examples include state channels, which allow participants to conduct transactions with each other outside the main chain, only settling on the base layer when necessary. Rollups are another innovative approach, aggregating multiple transactions into a single one to reduce the load on the main network. Sidechains also play a crucial role, functioning as independent blockchains with their own consensus mechanisms but ultimately tethered to the primary Layer 1 blockchain. These solutions are not merely theoretical; they are being actively implemented and used within the blockchain ecosystem — playing an instrumental role in the ongoing development and expansion of digital finance and applications.

As the blockchain industry evolves, the significance of Layer 2 solutions continues to grow. They are crucial to enabling the broader adoption of blockchain technology by improving transaction speeds and reducing costs, which are essential for user-friendly experiences and the efficient functioning of decentralized applications. By understanding Layer 2 blockchains and their role in the ecosystem, stakeholders can better navigate the complex landscape of blockchain technology and capitalize on the opportunities it presents for innovation and growth in various sectors.

Bridging from Layer 1 to Layer 2

Bridging between Layer 1 and Layer 2 blockchains is an essential process that allows transferring assets and data across different levels of blockchain architecture, enhancing the overall functionality and efficiency of the ecosystem. These bridges are vital for achieving interoperability, a key feature that enables disparate blockchain networks to interact and share information. By connecting Layer 1 blockchains, which serve as the fundamental infrastructure, with Layer 2 solutions that provide scalability and speed, bridges facilitate a more seamless user experience and support the growth of decentralized applications.

There are different types of bridges, such as trustless and trusted, each with its own mechanisms and use cases. Trustless bridges rely on smart contracts to automate the asset transfer process without intermediaries, thus offering a decentralized approach that aligns with the ethos of blockchain technology. On the other hand, trusted bridges depend on a central entity to oversee the transfers, potentially providing faster transactions but introducing centralization into the process. The choice of bridge type depends on the specific requirements of the transaction and the level of trust users have in the intermediary entities involved.

Blockchain bridges enable the transfer of tokens and cryptocurrencies between Layer 1 and Layer 2 and facilitate data sharing, which is crucial for maintaining the continuity and integrity of operations across networks. They provide the infrastructure necessary for Layer 2 solutions to thrive by leveraging the security and decentralized nature of Layer 1 blockchains. As the blockchain space continues to evolve, developing and implementing robust and secure bridging technologies will be pivotal in unlocking the full potential of blockchain scalability and interoperability, paving the way for a more interconnected and efficient future in digital asset management.

For example, if a user wanted to move ether or ERC-20 tokens from Ethereum to Arbitrum — a Layer 2 scaling solution that utilizes optimistic rollups — they could interact with the Arbitrum bridge contract on the Ethereum mainnet. The user would then send their tokens to this bridge contract, which locks them, effectively removing them from circulation on the Ethereum mainnet.

Once the tokens are locked, the Arbitrum bridge contract issues an equivalent amount of tokens on the Arbitrum network, which are then received in the user’s wallet on Arbitrum. These tokens are now available for use within the Arbitrum ecosystem, where transactions are faster and cheaper compared to the Ethereum mainnet.

Transactions on Arbitrum are batched and periodically committed to the Ethereum mainnet to ensure security and integrity. When the user wants to move their tokens back to Ethereum, they initiate a withdrawal request on the Arbitrum network. The equivalent tokens are then burned or locked on Arbitrum, and after a challenge period to ensure no fraudulent transactions took place, the tokens are released from the Arbitrum bridge contract on Ethereum.

Disclaimer: This article was produced with the assistance of OpenAI’s ChatGPT 3.5/4 and reviewed and edited by our editorial team.

© 2023 The Block. All Rights Reserved. This article is provided for informational purposes only. It is not offered or intended to be used as legal, tax, investment, financial, or other advice.

About Author

Adam is the managing editor for Europe, the Middle East and Africa. He is based in central Europe and was a managing editor and podcast host at the crypto exchange OKX's former research arm, OKX Insights. Before that, he co-founded, which he elevated into one of the leading crypto media brands at its peak as the editor-in-chief. Earlier, he served as the editor-in-chief at Before joining the blockchain and crypto industry, he worked for, and He tweets via @XBT002 and can be emailed at [email protected].