April 18, 2022

Developer AMA: Building the World’s First Cross-Chain NFT Marketplace

Axelar Team

As we’ve been going through applications to the Axelerator Grant Challenge, Axelar’s cross-chain developer grant


As we’ve been going through applications to the Axelerator Grant Challenge, Axelar’s  cross-chain developer grant program, a number of projects have stood out. One that we wanted to learn more about was AxelarSea, a cross-chain NFT marketplace developed by a team of builders at ContributionDAO. 

ContributionDAO is a Thailand-based group of developers, writers, marketers and researchers that invests its time, energy and expertise into projects it chooses. They have been contributing in various ways to Axelar, but AxelarSea stood out as an outstanding example of how builders can develop cross-chain apps using Axelar’s General Message Passing

AxelarSea is building to enable NFT holders to buy and sell on a cross-chain NFT marketplace, transacting from the blockchain of their choice, without stripping NFTs of the metadata that documents their origin and validity. Further, users will eventually be able to use their NFTs as collateral in DeFi applications and other more complex uses. Axelar’s General Message Passing makes this possible by allowing developers to call any function on any chain with permissionless proof-of-stake validation underneath. 

Read on below for an edited transcript of the Q&A between Axelar content lead Galen Moore, Axelar community lead Kate Stapleton and AxelarSea team members KTP and Mee, which took place live on Discord on Friday, April 15. And, learn more about the $2.3M Axelerator multi-chain grant program, here.   


Welcome everybody, to the live AMA between Axelar and AxelarSea, the first-ever cross-chain NFT marketplace. 


First of all, we’d like to thank the Axelar team for giving us a great opportunity to showcase what we’re building. You can call me KTP. I am a founder of AxelarSea, and I’m here with Mee, who is community lead on the project. 

AxelarSea is the first cross-chain NFT marketplace, including two key features. First is a cross-chain payment gateway. Second is a cross-chain NFT. Using our cross-chain payment gateway, a seller can list an NFT for sale from any chain and receive a payment from another chain. A buyer can buy an NFT from any chain. For the cross-chain NFT, we are able to bring the asset to any chain, while maintaining the data of the original minting operation. To do this we use General Message Passing by Axelar. 


That’s great, KTP. One thing I should mention as we, as we get started is that AxelarSea is an applicant for the Axelar grant program, which is open to applications through April 21. KTP and Mee, would you please tell us, what is the state of the NFT marketplace? What exists out there and what is the problem or gap that you’re trying to solve?


Thanks. Good question. Interoperability has been a problem in blockchain ecosystems from the beginning, but it is quite clearly a problem in NFT marketplaces. For example, on Opensea, the seller and the buyer need to be from the same chain. AxelarSea allows trading in NFTs from any chain to any other chain. 


For example, let’s say from the seller side, imagine that you have four different NFTs on four different chains, for example, Ethereum, Terra, Polygon and Solana. And you want to sell them. And what if it’s not just these four? The seller needs to go chain by chain to place their NFT on sale. To track their listings, they need to go through lots of marketplaces. And, their NFT will have quite a limited set of potential buyers, fragmented across all those chains. On AxelarSea, when you put an NFT for sale on any chain, buyers from any other chains can bid.

OK, let’s talk about from the buyer side. So imagine, let’s say you have some assets on Binance Smart Chain and you are going to buy an NFT on another chain. And what if you don’t have any assets on that new chain? You would need to look for a bridge that supports the asset transfer from BSC to that new chain. If you are not familiar with the destination chain, then you would have to learn how to use that new ecosystem, install the new wallet, find the best dex. And of course, you also need to fund that new wallet. You probably need to go to some centralized exchange to find some token to fund it. 

On AxelarSea, the seller can list their NFT, knowing that NFT will be exposed to buyers from any other chain, and that those buyers can bid on it with a one-click type of experience. So, for example, in our current testnet prototype, the seller can put the NFT for sale on Etherium, Avalanche, Fantom, Moonbeam and Polygon. The buyer can bid and to complete the transaction they don’t need to bridge assets cross-chain. We do that for them. They just simply click and buy. And then we do the cross-chain NFT transaction. We do the rest. So it’s just one click and done.

Cross-chain NFTs: current state


Very cool. So, tell us a little bit about how far you’ve come on this. The front end here looks great. If I wanted to come and list an NFT here for sale, is that, is that function available today? To what extent is the back end built out and where are you in the process of really making this a stable and full-featured release?


Yep, sure. Current status, we have built on testnet, and we spend two to four weeks on this version. According to our road map, we have five phases to complete, and this phase we get to showcase how cross-chain works. You’re welcome to try out and test the application.


Currently, if you want to put your NFT on sale, go to the website and simply connect your MetaMask wallet. You can click on the top tab to create. Right now, we haven’t allowed the NFT creator to upload their images yet. In the future, you can upload your own images. You can name it, you can do whatever you can do with a typical NFT. And so if you scroll down a little bit, thank you, in the case of the blockchains, you can choose any of the five blockchains that you want to mint your new NFT on. 

After your NFT is minted, you can place it on sale. On your profile page, we show your NFTs from multiple chains, meaning that you actually can track them quite easily. You can take them off the market, you could put them on the market again, you can adjust the price, from a single place. 

From the buyer side, we allow the buyer to buy from the Terra chain only. And so it means that you need to connect either Terra Station or Kepler wallet and fund it with testnet Luna. You can go to the explore page and you can select any NFT that you want and just click “buy now.” That should bring up the checkout page. Currently, we only allow a buyer to receive the NFT to the MetaMask wallet that is connected to the website. However, in the future, we would allow the buyers to actually choose which wallet they want to receive it in, and then click confirm. And that should complete the transaction. There will be a pop up from Terra Station to confirm that you actually want to pay. So we are really encouraging the community to actually try this out.

General Message Passing and cross-chain NFT metadata


We got a good question from somebody who’s joining the AMA here. User “Life Goes On”  asked what was the biggest challenge in developing the cross-chain NFT app? If you could talk a little bit about challenges, what was easy, what was hard, using Axelar to do this and other tools that you put into place as well?


That is a very good question. And I’m more than happy to share. I would have to say that certainly there are some hiccups along the way. But by and large we have had an enjoyable experience building on Axelar. The SDK provided makes the process really simple. For any developers listening, you definitely should try it out, for sure. 

Mainly, what we would like to see from Axelar is we would like to see a bit more detailed, documentation, especially more examples would be highly welcome. Apart from that, we feel really grateful for General Message Passing, which allows you to send state across chains with ease. To be honest, without General Message Passing, a cross-chain NFT marketplace is gonna be really hard to do.


We’re super excited about General Message Passing, as well. I think it’s the idea that you don’t have to move the asset to the program. You can move the program to the asset. It’s really what this grant program is all about. We’ve invited developers to “build the Web3 super app,” where you have all of the functions that a user would need inside one application. This is the kind of possibility that we envision for developers building using Axelar and it’s exciting to see the beginning phases of it here in the wild. 

So, with that in mind, tell me a little bit about next steps for AxelarSea. What’s your timeline and roadmap?

Cross-chain NFTs: timeline & road map


Uh, before we get the roadmap, I want to add a little bit more about General Message Passing. Usually when you bridge an NFT through the typical bridge, the NFT on the new chain is practically a new one. You can’t actually trace that NFT back to the original one, because when they bridge it, all the other information, let’s say the collection names and other metadata, are lost. The cross-chain NFT has become a new NFT. With General Message Passing on AxelarSea, in the future, if you bridge an NFT through AxelarSea, the dApp on the new chain would be able to trace the cross-chain NFT back to the original, minting chain to make sure that it is actually that NFT.

For example, let’s say you own an NFT on Ethereum and you take it cross-chain on AxelarSea to, say, Avalanche. The data of the NFT – the collection, the metadata – will be carried forwards, meaning that the dApp on Avalanche would be able to confirm that the NFT on the Avalanche is indeed coming from Ethereum. This novel solution using General Message Passing opens up unlimited possibility of usage. Like, for example, let’s say you can use your NFT on Ethereum as collateral on another chain, or you can create a dApp that utilizes NFTs from multiple chains, without worrying about the license or royalty fees problem or anything.


So you would envision – and I think maybe we’re talking very far-future roadmap here –  not only the ability to bring any NFT onto AxelarSea and sell it, but also the ability to do things like, as you mentioned, use it as collateral in a DeFi app on the same chain or on another chain, having all of those options at your fingertips, if you will.


Yes, absolutely. That is correct. Yeah. But just in the not-so-far future, for the upcoming quarter, we are aiming to complete the full functions of the cross-chain NFT marketplace. For example, like user can upload their own images, they can fully use the filters and, and they can see the full collections of the NFT. It’s gonna be just in between EVM chains first, and then after that, we’re gonna expand let’s say to the Cosmos ecosystem or some non EVM chains. The full version of the cross-chain NFT marketplace, we are aiming to launch probably between the third or the fourth quarter of this year.

Cross-chain NFTs: future possibilities in DeFi & beyond


I think this is one of the, the really exciting aspects of this, right, is the ability to not only move NFTs cross-chain, but then to be able to do DeFi with them, right? Take a loan out against your NFT. Fractionize your NFT from one chain on another. I think what this does for the industry as a whole, which is really exciting is it’s kind of an equalizer, right? Right now, a lot of the higher-value NFTs and projects are minted on Ethereum. And it’s not necessarily because the, you know, the, the 721 or the 1155 standard is superior to other chains, they’ve just been around longer. 

And then they have the marketplaces, like Opensea and Rarible, which get the high prices. So I think with cross-chain NFTs, it’s gonna really equalize the industry. Developers and artists through Axelar are able to build and create on the best platform, suited for their needs, without having to sacrifice liquidity from other chains or access to assets or markets on other chains.So, yeah, thanks for walking us through this. I’m really excited to see where this goes.


Where should people go to find out more about, AxelarSea?


We do have couple of social media. In the footer of our website at, you can find a link to our Discord channel, our Telegram channel, Twitter and YouTube. We are developing a bit of tutorials on YouTube and we are more than happy to answer any question that you might have as you play around with what we’ve built so far. 


I think there’s a couple more questions outstanding in the chat. We’re gonna try to answer those and not leave those hanging there, but with it being 1140 at this point, we want to let people get back to buidling what they’ve been buidling. So, thanks everyone for joining. Thanks to Mee and the entire AxelarSea team for presenting here and for, for building this exciting project.


Yeah, definitely. So if anyone still have a question and, and we might have not answered it in this call, come to our Discord or Telegram and we are more than happy to help you there.


Great. And just to put in one final plug for the Axelar grant program, go to our website and in the developers tab at the top nav, the information is right there. We’re open for applications through April 21. Let us know what you’re building and how we can help you take it cross-chain.

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