Three years after Bitfinex covered Ark as an unimplemented proposal, two different implementations — Ark Labs’ Arkade and Second’s Bark — are now live on Bitcoin mainnet and gaining real-world traction, with interest in similar approaches now spreading well beyond the teams that built them.
A lot has changed since Bitfinex last discussed Ark in 2023. What back then was an ambitious albeit unimplemented proposal for simplifying self-custodial Bitcoin payments has now become working infrastructure, with Ark Labs’ Arkade and Second’s Bark both operating on Bitcoin mainnet.
The two implementations represent different approaches to the same underlying architecture. Arkade is exploring how the model can support not only bitcoin payments, but also assets, swaps and more complex financial applications. Bark is focused on improving self-custodial bitcoin payments and Lightning interoperability.
The emergence in July 2026 of Wavelength, Lightning Labs’ alpha-stage toolkit built around an “Ark-like settlement layer” for agentic payments, has also brought attention to similar approaches beyond the teams directly building Ark implementations.
Like RGB, which Bitfinex recently examined as another approach to expanding Bitcoin’s capabilities without changing the base layer, Ark reflects a broader trend in Bitcoin development towards building specialised systems around Bitcoin while preserving its role as the underlying settlement layer.
What Has Changed Since 2023?
Ark was first proposed in 2023, promising to let users send and receive self-custodial bitcoin without needing to open Lightning channels, source inbound liquidity or operate an always-online node.
It achieved this through virtual transaction outputs, or VTXOs: off-chain, pre-signed Bitcoin outputs backed by bitcoin committed in a single bitcoin transaction.
Bitcoin normally records ownership through unspent transaction outputs, or UTXOs. Spending bitcoin means consuming existing outputs and creating new outputs controlled by the next owner. Ark extends this model by allowing users to transfer VTXOs off-chain while maintaining a route back to Bitcoin settlement.
In the original Ark proposal, the entity coordinating transactions, VTXO renewal and entry and exit from the protocol was called an Ark Service Provider, or ASP. Arkade and Bark have since taken different approaches to this role, with one or multiple operators providing the coordination needed for the creation and execution of Virtual UTXOs.
Ark’s key distinction from custodial payment solutions is that users do not simply hold a balance controlled by the coordinating service. Instead, each VTXO includes a pre-signed exit path that allows its owner to recover the underlying bitcoin on-chain if the service provider becomes unavailable or refuses to cooperate.
The original Ark design was closely associated with covenant functionality that Bitcoin does not currently support, raising early questions over whether the architecture could be implemented without changes to Bitcoin’s consensus rules. Since then, Arkade and Bark have demonstrated that many of Ark’s core ideas can be built using existing Bitcoin primitives, including pre-signed transactions and collaborative signing.
Ark has not developed into one single network. Because interoperability between different Ark Service Providers is not a requirement of the architecture, different implementations can evolve independently. Payments between users of different implementations can typically route through Lightning instead.
This reflects a broader pattern in Bitcoin development. Lightning, Liquid, Spark and BitVM all extend Bitcoin in different ways without requiring one shared architecture. Bitcoin Optech tracks Arkade and Second’s implementation as distinct systems rather than versions of one network, while the March 2026 V-PACK proposal aims to provide a neutral format for verifying and backing up VTXOs across different implementations.
Arkade processed its first mainnet payments at the Baltic Honeybadger conference in August 2025 before opening publicly that October. Second brought Bark to Bitcoin mainnet on 9 June 2026, with a public server, developer SDK and integrations spanning mobile wallets, an Umbrel application and a BTCPay Server plugin.
Both implementations address similar challenges around fast off-chain payments. Second uses arkoor transactions, allowing transfers to occur outside scheduled rounds with coordination from the Ark server. Arkade achieves the same functionality through its Virtual Mempool architecture.
Financial Applications Built Around Bitcoin
Arkade’s broader ambition is to extend the VTXO model from a payment mechanism into a more general execution environment around Bitcoin.
In practice, this means transactions can be validated and coordinated off-chain before later settling to Bitcoin, rather than requiring every individual transfer to wait for its own on-chain confirmation.
This separation between execution and settlement introduces a different architecture from Bitcoin’s base layer. Users retain a unilateral exit path for the underlying bitcoin, while Arkade’s signer infrastructure coordinates preconfirmed transactions before they are ultimately settled on Bitcoin.
Arkade uses Trusted Execution Environments (TEEs) and remote attestation to allow users to verify aspects of the environment running the signing software and provide greater assurance that it is operating as intended.
The clearest extension beyond Bitcoin payments is Arkade Assets, introduced in October 2025.
Arkade Assets extends the VTXO structure used for bitcoin transactions to support fungible assets such as stablecoins, allowing them to move through the same broader execution environment. Bitcoin secures the underlying VTXO structure and unilateral exit path for bitcoin held within Arkade, while their guarantees depend on the asset protocol and the rules established by the issuer. More complex contract tooling is being developed with a future view towards applications such as lending and trading.
This places Arkade within the broader ecosystem of Bitcoin asset protocols, alongside approaches such as RGB. The two systems take different paths to a similar challenge: expanding what can be built around Bitcoin without requiring the base layer to execute every application directly.
RGB uses client-side validation, where participants independently verify the asset state relevant to them. Arkade instead uses a shared off-chain execution environment, with transactions coordinated before later settlement to Bitcoin.
By combining assets, payments and programmable transaction flows, Arkade is exploring infrastructure that could support applications including stablecoins, swaps, collateral arrangements and other financial workflows.
One concrete example is Lendaswap, a non-custodial swap product launched by Lendasat (now Satora) in November 2025 that uses Arkade to facilitate swaps between bitcoin and stablecoins on other chains. Similarly, in May 2026, Hodl Hodl, the peer-to-peer Bitcoin exchange, integrated Arkade into its escrow system to speed up trade settlement.
The following month, Bitrefill added Arkade as a payment option on its gift card platform, offering instant, zero-fee purchases.
Commercial interest has also emerged around this direction, with Ark Labs raising $5.2 million in a March 2026 funding round backed by Tether, alongside investors including Ego Death Capital, Epoch VC and Anchorage Digital.
A Broader Bitcoin Infrastructure Stack
Ark’s evolution reflects a wider shift in Bitcoin development: building specialised systems around the base layer while preserving Bitcoin’s role as the final settlement layer.
Ark Labs is building VTXO architecture that can support bitcoin plus a broader range of financial applications, including assets and programmable transaction flows. Second is continuing to refine Bark around self-custodial bitcoin payments and Lightning Network interoperability. Meanwhile, Wavelength suggests that Ark’s settlement designs are gaining attention beyond the original Ark ecosystem.
Three years ago, Ark was an ambitious proposal for making self-custodial Bitcoin payments simpler without changing Bitcoin itself. The open question was whether its architecture could move from theory into practice. Today, that question has been answered. Ark is live, multiple implementations exist, and developers are now exploring how the same VTXO-based model can support not only faster payments but a broader layer of Bitcoin-native financial infrastructure.
