It’s here, BOSes!
We are thrilled to announce the launch of the BitcoinOS Grail testnet bridge app, allowing users to move Bitcoin from Bitcoin Testnet 3 to a variety of EVM-based testnets. This marks an exciting milestone for BitcoinOS as we bring our technology closer to users and developers.
As of today, anyone can access the app here on desktop (mobile integration coming soon).
In this first iteration, the bridge showcases only a fraction of the technology behind BitcoinOS. Currently, the app enables Bitcoin-to-EVM transfers, a capability we first demonstrated in November last year with a successful Bitcoin-to-Merlin transaction. For those interested in the technical details of that transaction, we have comprehensive explainers available here.
Why This Matters
BitcoinOS has always aimed to push the boundaries of what's possible with Bitcoin. While our technology has often seemed abstract, this testnet bridge provides a tangible tool for users and builders. Now, anyone can access our bridge app, get testnet 3 BTC from the faucet, and transfer BTC to various EVM testnets without needing to worry about gas fees, which we are currently subsidizing. All transactions are on testnet so there will be no monetary value associated with it.
Details of the Testnet
Disclaimer: Bitcoin testnet 3 will be decommissioned relatively soon and we will transition our system over to testnet 4. In the meantime, there might be issues with mobile wallet usage on testnet3 or other back-end issues. None of the funds used in this exercise is real.
Go to the testnet bridge here: https://test-grail.bitcoinos.build/
Go to the BTC testnet 3 faucet to get the testnet BTC that you will bridge.
Connect your wallet on the testnet bridge and select the destination chain to which you want to send your test BTC!
Switch networks on your wallet and you should see the newly bridged testnet BTC appear!
The testnets that we’ve initially integrated with are:
- From: Bitcoin testnet 3 (this will be moved to testnet 4 eventually)
- To:
- Ethereum Holesky
- Merlin Testnet
- Mode Sepolia (find testnet info here
- Base Sepolia
We will be supporting a few existing wallets to begin with
- OKX wallet (desktop and eventually mobile)
- Xverse (desktop)
- Unisat (desktop)
- Leather (desktop)
- BitGet (desktop)
- All Wallet Connect-supported wallets
The destination chains currently supported are all EVM-based. This focus is intentional: EVM chains host approximately 90% of all DeFi activity and the majority of wrapped BTC. Our core team prioritized EVM integrations for this reason. However, once we have this architecture nailed down for the system we are going to start working with our key partners to integrate this system across to non-EVM chains.
Although the current demo only supports one-sided BTC transfers, our internal development is already further along. Soon, we aim to integrate a prover to enable two-way bridging, allowing users to move funds back to Bitcoin. By the end of the quarter, we hope to facilitate mainnet transactions.
How the BitcoinOS Bridge Works
At first glance, the interface might resemble a typical swap or bridge app, but the real innovation lies beneath the surface. Here’s a simplified breakdown of how the fully operational system will function:
- Depositing Bitcoin: Users lock BTC in a Taproot address on Bitcoin.
- Proof Generation: A zk-proof verifies the locked BTC.
- Minting on Destination Chain: The bridge mints an ERC20 version of BTC on the destination EVM chain, maintaining a 1:1 peg.
- Withdrawing Bitcoin: To withdraw, users burn the ERC20 BTC on the EVM chain and present a zk-proof of this burn to the BitcoinOS validator network.
This is where BitcoinOS stands out. The validator network, consisting of BOS nodes, verifies the zk-proof. Unlike traditional bridges relying on consensus, zk-proof verification is like solving a math problem—there’s a definitive answer. Even a single honest node ensures the bridge’s integrity, making it more secure than designs dependent on majority consensus. This is why our system only needs one honest node to operate with integrity. Other systems need to make sure there is always an honest majority present.
Why BitcoinOS Bridge is More Secure
Our bridge design enhances security with minimal trust assumptions:
- Non-custodial security: BTC is never held by a third party.
- Bitcoin-native security: All transaction states and verifications are posted back to Bitcoin.
- Decentralized validation: The validator network can grow permissionlessly, making the system more and more expensive to take over and requiring only one honest node to prevent fraud.
This approach offers Bitcoiners the trust and security they value while enabling cross-chain functionality.
Get Started with the Testnet Bridge!
Head to our testnet bridge app to start transferring Bitcoin to EVM testnets. We provide detailed instructions, FAQs, and support through our Discord and Telegram channels.
We’re also launching campaigns around testnet tasks, so stay tuned for opportunities to get involved and earn rewards!
This is just the beginning. More testnets and exciting ecosystems are coming soon. Join us as we continue to build and expand BitcoinOS to bring secure, non-custodial, cross-chain functionality to Bitcoin.
Visit our testnet bridge, explore, and help us shape the future of Bitcoin interoperability!
