Native Bridges vs. Third-Party Bridges: What’s Right for Your Rollup?

Bridges are one of the most important components of your rollup’s infrastructure. They’re the primary means of onboarding to your chain, and have a huge impact on the chain’s security, user experience, and more. 

The key question for rollup builders when it comes to bridges is this: Should you rely solely on the native bridge of your rollup development framework, or should you integrate a third-party bridge? 

Widely used rollup frameworks like OP Stack and Arbitrum Orbit come with battle-tested native bridges that give your chain a reliable connection to Ethereum and can function as your primary onboarding mechanism. However, native bridges also have shortcomings like slow withdrawal times and a lack of connectivity with other rollups. But third-party bridges come with their own risks, not to mention the costs of integrating an external piece of infrastructure. 

In this blog, we’ll dive into the pros and cons of native bridges vs. third-party bridges, and tell you when and why third-party bridges might be appropriate for your rollup. 

The role of bridges in rollups explained

Bridges are the crucial infrastructure that connect separate blockchains, allowing assets and data to be transmitted between them. Bridges are especially important for rollups, as they connect the chain to the L1 that it’s built on top of, which we’ll assume to be Ethereum for the purposes of this article. Most of your users will likely be pre-existing Ethereum users who deposit ETH or other ERC-20s to your chain via the bridge, meaning that the bridge is your primary onboarding mechanism and therefore crucial to growth. Without a bridge, there’s virtually no way for users to move assets to your rollup. 

There are other roles that native and third-party bridges can fulfill for your rollup, which we’ll cover in-depth later. But first, there are a few core requirements any bridge you use has to meet regardless of whether it’s native or third-party:

• Reliable asset transfer. First and foremost, the bridge needs to enable the successful transfers of assets between your rollup and the other chains it connects to — most importantly Ethereum — on a consistent basis. 
• Data integrity. Bridges also need to ensure that data like wallet balances and smart contract state is reflected accurately between the rollup and the other chains it connects to. This is important for things like preventing double spend and ensuring apps that exist on both chains stay in sync.
• Rollup security. As a central point that assets travel through and are often locked in for extended periods of time, bridges are crucial to security for your rollup. For instance, if assets deposited to your bridge on Ethereum aren’t secure, then all of the assets they back on your rollup can be rendered worthless. Native bridges specifically are also often closely tied to the rollup’s security model. Rollups built on the OP Stack and Arbitrum, for instance, rely on fraud proofs for users to challenge and reverse invalid state transitions on the rollup before they’re committed to Ethereum. Those mechanisms rely on the native bridge to function. 
• User experience. Virtually every user will need to interact with a bridge to onboard to your rollup, so it’s important that they’re easy to use. This necessitates strong onchain infrastructure to enable fast, frictionless bridging transactions, as well as an intuitive front-end for users to interact with. 

Any bridge your rollup relies on needs to fulfill those key roles. 

Native bridges vs. third-party bridges for rollups

In the context of rollups, bridges generally come in two varieties:

Native bridges are the bridges that come pre-built into the architecture of the rollup framework you use to build, and are maintained by the team behind that framework. For instance, the native bridge for OP Stack rollups is Optimism’s Standard Bridge, while the native bridge for Arbitrum Orbit rollups is the Arbitrum Bridge. 

Third-party bridges meanwhile are bridges built by another provider, and that can integrate with your rollup, in addition to other rollups and Ethereum itself. Popular third-party bridge providers include LayerZero, Relay, Decent, and Hyperlane, all of which are available for rollups on Conduit Marketplace.

Let’s dive more into the pros and cons of native and third-party bridges below.

Native bridge pros and cons for rollups

Native bridges are built from the ground up to work with chains deployed using your rollup development framework. Native bridges have been battle-tested by the primary mainnets associated with those rollup frameworks — that is, Optimism Mainnet for the OP Stack and Arbitrum One for Arbitrum Orbit — as well as the many other chains in those frameworks’ respective ecosystems.

That standardization and security translates to several benefits for rollups.

Pros of native bridges for rollups:

• Inherent alignment with your rollup. Native bridges are designed to operate in tandem with your rollup, which generally means there’s less chance of users encountering errors. This also makes the native bridge the best choice for security, as your rollup’s fraud proof systems, consensus mechanisms, and transaction validation processes are designed to rely on the native bridge by default.
• Simplified trust model. The native bridge doesn’t require your rollup to make any security assumptions you aren’t already making based on the development framework you use. You don’t need to take on any additional validators, liquidity providers, or external consensus mechanisms, which reduces the number of security vulnerabilities and centralization risks.
• Ready out of the box. The native bridge is simply the easiest to deploy and maintain since it comes with your rollup by default. Plus, it undergoes regular maintenance from the same team you already rely on to upgrade your chain, which means future changes to the rollup framework are unlikely to cause compatibility issues with the native bridge. And, while native bridges are in some ways a one-size-fits-all option, you can still customize their UI with tools like Superbridge, which is available to integrate with your rollup on Conduit Marketplace.

While native bridges are considered safer and easier to use, they also lack some of the functionality that third-party bridges bring.

Cons of native bridges for rollups:

• Slow withdrawals due to seven-day challenge period. On rollups built with the OP Stack and Arbitrum Orbit or Nitro, there’s a seven-day challenge period during which transactions can be disputed before they’re committed to Ethereum. That means withdrawals from your rollup to Ethereum take seven days to execute, which introduces a point of friction for users. However, new developments that we'll explore below have made this issue possible to overcome while using the native bridge.
• Only connects your rollup to Ethereum. While native bridges enable a strong, reliable connection to Ethereum, that’s the only connection available. Native bridges can’t connect your rollup to other L2s and L3s, which takes away flexibility from your users.

While the seven-day withdrawal waiting period is the major con of native bridges, recent developments have made this possible to overcome while sticking with the native bridge. For example, Arbitrum recently introduced fast withdrawals for some Arbitrum Orbit rollups, depending on their configuration. Arbitrum fast withdrawals allows rollups to process user transactions with a committee of validators, and offer withdrawals to Ethereum in as little as 15 minutes provided the committee's validation is unanimous. On the OP Stack, rollups can now implement ZK proofs for fast finality using OP Succinct, a zkEVM developed by Succinct Labs that can be integrated into the rollup's infrastructure.

Third-party bridge pros and cons for rollups

For rollups, third-party bridges primarily exist to solve the two problems of native bridges that we describe above — slow withdrawals and lack of connection to chains other than Ethereum. 

Pros of third-party bridges for rollups:

• Instant withdrawals. Third-party bridges enable users to avoid the impact of the seven-day challenge period and withdraw assets from your rollup faster than is possible on the native bridge. They do this by maintaining liquidity pools for supported assets on the two chains, allowing the bridge to fund the user’s address on the second chain with funds equivalent to the withdrawal before the challenge period is done. In this way, the third-party bridge takes on the risk of transactions being invalidated during the challenge period. Third-party bridges can attempt to mitigate that risk through their own expedited transaction validation processes, or through other insurance tactics. 
• Rollup-to-rollup connections. While native bridges only enable transfers between your rollup and Ethereum, third-party bridges can enable transfers between your rollup, Ethereum, and other rollups as well. This enhanced flexibility can improve user experience and further incentivize users to transact on your chain.

The benefits of third-party bridges, however, also come with increased risk in other areas.

Cons of third-party bridges for rollups:

• New sources of risk. When third-party bridges introduce external components like outside liquidity providers or bonded relayers to facilitate withdrawals, those components become additional entities users must put their trust in when using your chain. Similarly, if third-party bridges connect your rollup to a new chain other than Ethereum, you’re now relying on smart contracts on the new chain to back some of the assets on your rollup.
• Greater complexity. Third-party bridges aren’t designed to work specifically with your chain the way your native bridge is. This may increase operational complexity, and require you to expend resources both when setting up the bridge and when maintaining it in the future. 
• Service costs. Third-party bridge providers will generally charge you a fee to integrate the bridge with your rollup, and may also charge ongoing transaction fees to you and your users.

While third-party bridges introduce many benefits that native bridges don’t have, you have to decide if those benefits outweigh the risks and costs.

When should you use a third-party bridge?

The question of whether to integrate a third-party bridge comes down to your chain’s use case, and whether the benefits of faster withdrawals and interoperability mean more to your users than the risks third-party bridges introduce.

For instance, if your chain is geared toward high-volume traders who want the option to shift funds quickly between many chains, then a third-party bridge would be attractive to them. But if your chain’s use case calls for users to keep funds on your chain for a long time, such as by offering long term staking opportunities or hosting a game that calls for extended play, then a third-party bridge won’t offer as much benefit. 

You also have to consider where your potential users are. Ethereum Mainnet is the center of the EVM ecosystem, so for most new rollups, the users you’re targeting likely have funds on Ethereum that they can bridge to your chain. However, if you have reason to believe that your chain can attract users who currently keep most of their funds on another rollup, then you should consider adding a third-party bridge that can support transfers from that rollup.

Ultimately, cost-benefit analysis will lead many rollups to integrate a third-party bridge, especially over time as the rollup ecosystem grows and more users look to onboard from chains other than Ethereum. Rollup teams at that point must evaluate the individual third-party bridge providers to identify the one most compatible with their chain. Regardless, the native bridge will always remain as an important part of your rollup’s security processes and a reliable means of maintaining a connection to Ethereum — for many rollups, that may be the only bridge solution necessary.