Ethereum L2s will be interoperable ‘within months’: Complete guide

Ethereum is finally on the verge of solving the interoperability problems that have plagued the ecosystem since the layer 2 roadmap started to take off a couple of years ago.

This year, users can expect to see easy crosschain swaps between L2s, new chain-specific addresses that are human-readable, trustless crosschain messaging and the launch of innovative “unified liquidity” bridges like Polygon’s Agglayer.

With the first of the upgrades going live in the next few weeks, ecosystem leaders from Base to Across predict it’s only a matter of time before Ethereum will feel like Ethereum again.

“The move toward fast, standardized interop isn’t just a technical upgrade — it’s essential for making Ethereum feel like one seamless ecosystem,” explains Across co-founder Hart Lambur.

“When chains can interact in two seconds or less, the vision of a unified Ethereum comes to life.”

Lambur revealed that the audited code for Across and Uniswap’s new intent standard (EIP-7683) will be deployed within the next week, with crosschain orders starting to flow through the decentralized solvers system “in the coming weeks.” Fifty projects and protocols are supporting the new standard, including Polygon, Arbitrum, Optimism, Base and Uniswap.

Ethereum interoperability: What’s changing in 2025

In the last bull run, Ethereum had a scaling problem. Gas fees peaked at $200 per transaction as a deluge of users competed for blockspace. Layer 2 rollups like Base, Arbitrum and Optimism emerged to fix that issue and have successfully scaled transactions by 15 to 20 times, with fees now counted in cents.

Unfortunately, it’s left Ethereum with 55 new rollups that are all effectively isolated from one another. Users have to muck around with expensive and risky bridges to move between them. The lack of cohesion and interoperability has weighed heavily on ETH sentiment and price.

Mallesh Pai, the senior director of research at Consensys, says the first piece of the interop puzzle to be solved will be enabling simple crosschain swaps between tokens on different L2s.

“I think what we’ll get in the next few months will be seamless token transfers,” he tells Magazine, noting that’s still some way away from synchronous composability — where every app and every L2 offers complete and instantaneous interoperability — but it’s still good enough for “99.9999%” of what most users need.

“Most of our users, they have their money on one chain, they want to buy something on another chain. And I believe we’ll be able to deliver that in months.”

Base lead contributor Jesse Pollack told Magazine at Devcon that two particular improvement proposals stand out for the impact he expects them to have.

“It’s getting solved fast. There’s two really important specifications that are being worked on right now. One is called ERC-7683, which kind of defines these standards for these intents, which is a form of crosschain execution,” he says.

“And then the one that we’re helping drive called RIP-7755, which basically lets you execute crosschain transactions really easily.”

RIP-7755 interoperability plan explained

Rollup Improvement Proposal-7755 uses a permissionless network of offchain relayers called Fulfillers, who earn a tip for ferrying a user’s crosschain call to the correct destination.

“It lets you execute a transaction from one L2 on another L2 in a totally trustless way. And so you can execute it over there, and then you can kind of have the balance settle back to the original place and there’s no third party,” he says. “It just relies on the existing Ethereum construction.”

Emmanuel Awosika, head of research from 2077 Collective, says one of the advantages of this approach is that it “allows bridging via lock/mint of tokens across chains” which he says is superior to using liquidity pools.

Because the different L2s all have different block times, the transactions won’t be instant (known as “synchronous”), but they’ll be pretty fast. This is called “asynchronous,” and Pollack doesn’t think the brief delay will be an issue.

“If you look at the internet, it’s predominantly asynchronous today, like, that’s the way you scale by not having tightly coupled dependencies. And that’s how we think Ethereum is gonna scale as well.”

He predicts a future where you can do whatever you want, without worrying about which chain you are on.

“It’ll instead just be your wallet that lets you work everywhere. And then from there, we’ll expand to all the other L1s so that you can have your assets on Base and you can transact everywhere.”

Across and Uniswap’s crosschain intent standard (ERC-7683)

Traditionally, crosschain bridging has involved sending funds to a smart contract where it gets locked up, with the bridge on another chain releasing the corresponding funds. This has issues with speed, costs and security.

More recently, intents-based bridges have become popular, like Across Protocol, which launched in 2021. Intent refers to users expressing a high-level goal — “swap token X on Optimism for token Y on Polygon” — and then a bunch of ‘solvers’ compete to work out the most efficient way to make it happen.

Across, which is also integrated with UniswapX, has a decentralized network of 30 or so solvers (AKA market makers/fillers/relayers), who quickly fill the user with their own funds on the destination chain and take on the finality risk. Swaps take an average of about three seconds.

Awosika explains a key difficulty for these types of systems is accessing sufficient liquidity for every coin because every app has a different group of solvers.

“There’s a problem currently where different solver networks are fragmented because each protocol has a different method of handling intent creation, execution, and settlement,” explains Awosika.

Across teamed up with Uniswap — about to launch its own L2 called Unichain — to propose ERC-7683, which operates a little like an order ticket that you might hand to a stock broker. The standard formalizes what information is sent out from protocols so that any solver in the decentralized network can pick up the order and execute it.

That means that instead of everyone having small, separate networks of solvers, a larger group can now take standardized orders from any app or protocol. Intents can handle crosschain transactions like token swaps, NFT transfers, and governance votes.

While users will see an immediate benefit, with all the crosschain difficulties abstracted away, intents-based systems will benefit greatly from further interoperability improvements.

“We’re actively working with the Superchain, AggLayer and Arbitrum teams to leverage their messaging systems for ERC-7683,” Lambur explains.

The AggLayer and other Ethereum interoperability solutions

Polygon’s AggLayer hopes to not only solve interoperability between all of the Ethereum L2s but, one day, all of the smart contract chains too, connecting up the disparate blockchains in the same way that TCP/IP connected up the internet. 

Polygon co-founder Brendan Farmer says the AggLayer will help the solvers in getting your transaction where it needs to go. He uses the analogy of a plane trip to explain how.

“It’s like you’re taking a plane ride, and right now, with intents and solvers, it’s like you can’t bring your suitcase on the plane, and so you’re basically just bringing money and then a list of all your possessions, and then you hand it to the concierge at your destination and he buys all your stuff. Whereas with the AggLayer, it’s like you’re able to bring your suitcase.”

Also read: Pectra hard fork explained — Will it get Ethereum back on track?

The AggLayer site describes it as a neutral, crosschain settlement layer that unifies liquidity and users and posts finality to Ethereum.

“The AggLayer’s biggest feature is using a shared bridge that all AggLayer rollups deposit into. This is different from the status quo where different rollups have their own bespoke bridge on Ethereum L1,” says Awosika.

Having all the assets in the same bridge and using ZK “pessimistic” proofs to validate whatever claims are made, supports efficient crosschain transfers with minimal overhead. Instead of having to check if a transfer is valid by looking up two different chains, all the funds are in the same pot. That means, in many cases, the coins don’t even need to move, and the record of who owns what can simply be updated.

The AggLayer v0.2 mainnet went live this week and will integrate the Polygon chains and projects from Movement Labs, Near, OXK X Layer and Ton Application Chain, with crosschain transfers beginning around March or April.

Agglayer is intended to scale all of web3, not just Ethereum.

What do people value in web3? Assets.

There’s always going to be assets outside of Ethereum.

So a big part of the Agglayer is bringing everything together and ultimately having finality on Ethereum. pic.twitter.com/3RcwcolRJ5

— Polygon (※,※) (@0xPolygon) November 25, 2024

“We plan on deploying Agglayer contracts to every major chain,” he says. Agglayer doesn’t work as well with optimistic rollups right now due to the seven-day withdrawal period, but rollups on the OP Stack could integrate ZK-proofs viaOP Succinct.

Farmer says the AggLayer allows for the trading of native tokens rather than wrapped versions.

“I think it’s just solving these problems of unified liquidity and fast interoperability and so that’s like the ability to bridge assets and not worry about paying market makers to swap or worry about having seven different types of ETH for all the chains that you use. It’s this experience that feels like using a single chain, even as you’re traversing boundaries between different chains.”

Chain-specific addresses… that are human-readable! (EIP-3770, EIP-7828)

Another upgrade (EIP-3770) will identify which EVM chain a particular address belongs to. “This will prevent the problem where someone does something like send funds to a particular smart contract wallet that doesn’t exist on a particular chain,” Awosika says.

The new addresses will still look like a meaningless jumble of letters and numbers though, so another EIP (7828) goes one better and blends chain-specific addresses with the Ethereum Naming Service. 

So you’ll end up with an address that looks like Andrew@optimism.eth. According to the “L2 interop working group” call on Jan. 29, the “finishing touches” are being put on this EIP.

Smart Accounts in the Pectra hard fork (EIP-7702)

The Pectra upgrade in March includes EIP-7702, which turns ordinary externally-owned accounts accounts into smart accounts.

Also read: They solved crypto’s janky UX problem — you just haven’t noticed yet

One benefit is enabling apps or wallets to sponsor gas fees, which can grease the wheels of a crosschain transaction.

“If I want to bridge from Optimism to Arbitrum today, I may need to pay ETH on both chains to complete the transaction,” says Awosika. “Since I’m bridging to Arbitrum for the first time, I may not have ETH there — a paymaster can just pay the gas fee on my behalf, credit my address, and take a cut of the transfer as payment for the service.”

The future of Ethereum interoperability: Native and Based Rollups

While basic interoperability is being solved this year, there are refinements being worked on to improve the process even further.

Ethereum devs are working hard to realize single-slot finality, which allows blocks to be proposed and finalized within 12 seconds rather than 15 minutes and means transactions are confirmed almost instantly.

“SSF is a big blocker for rollup interoperability,” says Awosika. Solvers currently take on the risks associated with unconfirmed transactions for 15 minutes, so cutting that down to seconds will offer a big improvement.

And in future shared sequencing, based and native rollups have the potential to make the entire ecosystem interoperable and composable in real-time — meaning everything would work seamlessly with everything else.

That goal became a lot more realistic after a recent call in which the leaders of L2s, including Base, Arbitrum and Optimism, agreed to implement based or native rollups (both of which use the L1 more extensively). These systems do offer the prospect of synchronous composability in the ecosystem, but the bugs will take some time to iron out.

Based rollup Taiko, which uses Ethereum’s validators for sequencing, is already up and running. 

Declan Fox, product lead at zkEVM L2 Linea, tips we’ll see new based rollups launching this year but says it will take time to convert existing L2s, and new standards will need to be developed to make them interoperable.

“Linea is supporting ENS Namechain to explore launching as a based rollup this year; however, migrating existing L2s with large ecosystems will more likely be seen in 2026,” he says.

Fox notes that native rollups require a hard fork of the L1 to “introduce the new precompile; therefore, with the priority around scaling blobs, I would expect it to be included earliest 2026.”

Another approach to interop comes from Espresso, which offers a shared sequencer to the L2s and integrated the Arbitrum L3 Rari on Jan. 31.

Farmer says he hopes to hook the Agglayer up to Espresso by the end of the year. 

“So you can have the holy grail for L2s which is synchronous composability. So this is where blocks for different chains are being built by the same entity at the same time,” says Farmer.

“You can deploy a contract that can make synchronous calls to contracts that are deployed on entirely different chains, and users can use all of those and constantly access the best execution for their trades and the deepest liquidity.”

“And so it stitches together this ecosystem that’s currently fragmented of L2s on top of Ethereum into something that feels like using Ethereum itself, or using a single chain.”

This article first appeared at Cointelegraph.com News