Bitcoin Multisig Services: Unchained vs Casa vs Nunchuk

Bitcoin Multisig Custody Services Compared

A multisig wallet requires multiple private keys to authorize a Bitcoin transaction. Instead of trusting a single device or seed phrase, multisig distributes risk across separate keys held in different locations, on different hardware, or by different parties. The result is a custody model where no single point of failure can compromise your funds.

Several companies now offer managed multisig services that handle the complexity of key coordination, wallet configuration, and inheritance planning. These range from fully managed platforms like Unchained and Casa to privacy-focused tools like Nunchuk, and from free open-source coordinators like Caravan to full DIY setups in Sparrow Wallet. The following table summarizes the key differences.

For a deeper look at how multisig compares to MPC-based custody, see our MPC vs multisig custody analysis. For help choosing between specific hardware devices, see the multisig setup comparison tool.

Key Configuration and Architecture

The way each service distributes keys determines both security and convenience. In a collaborative custody model, the service provider holds one or more backup keys but never enough to unilaterally move funds. You retain enough keys to spend without the provider's involvement.

Unchained: 2-of-3 Collaborative Custody

Unchained uses a 2-of-3 configuration where you hold two keys on separate hardware wallets and Unchained holds one backup key. You can sign transactions using your two keys without Unchained's involvement. Unchained's key serves as a recovery backstop: if you lose one of your devices, you can use your remaining key plus Unchained's key to move funds while you set up a replacement.

Casa: 2-of-3 and 3-of-5

Casa's Standard plan ($250/year) uses a 2-of-3 setup. You hold two keys: one on a hardware wallet and one on the Casa mobile app. Casa holds a third recovery key. The Premium plan ($2,100/year) upgrades to 3-of-5, distributing keys across multiple hardware wallets, the mobile app, and Casa's recovery key. Premium members receive a welcome package with hardware devices, Faraday bags, and tamper-evident bags. Casa also offers a Private Client tier with custom pricing for institutional needs.

Nunchuk: Flexible Quorums

Nunchuk's free tier supports fully DIY multisig with any quorum configuration. The Iron Hand plan ($120/year) provides assisted 2-of-3 multisig where Nunchuk holds one platform key. The Honey Badger plan ($480/year) uses a 2-of-4 setup where you control three keys (two regular plus one dedicated inheritance key) and Nunchuk manages a fourth. The Honey Badger Premier plan ($2,100/year) upgrades to 3-of-5 with three wallets and two inheritance keys. Nunchuk also supports Taproot multisig using Schnorr signatures and MuSig2, which reduces on-chain fees and improves privacy by making multisig transactions indistinguishable from single-sig on the blockchain.

Caravan and Sparrow: Full DIY

Caravan is a stateless, browser-based multisig coordinator built by Unchained. It supports quorums up to 7-of-N and works with any hardware wallet that produces PSBTs. Because Caravan is stateless, it stores no wallet data between sessions: you re-enter your extended public keys each time. Sparrow Wallet is a full-featured desktop application supporting up to M-of-15 cosigners, with persistent wallet state, coin control, and air-gapped signing via SD card or QR code.

Hardware Wallet Compatibility

The hardware wallets you can use vary by service. The following table maps device support across each platform.

Sparrow has the broadest hardware wallet support of any Bitcoin coordinator, including air-gapped workflows via SD card and QR code. Nunchuk stands out on mobile with NFC support for TAPSIGNER, making it the most accessible option for signing on a phone. Casa uniquely supports YubiKey security keys as Bitcoin signing devices. For a full breakdown of hardware wallet features, see the hardware wallet comparison.

Inheritance and Estate Planning

Inheritance is one of the primary reasons people choose managed multisig over DIY. Without a plan, Bitcoin held in self-custody can become permanently inaccessible if the owner dies or becomes incapacitated. For a comprehensive overview, see our Bitcoin inheritance planning guide.

Unchained offers a dedicated Inheritance Protocol: a package of documents and instructions that an executor can follow without Bitcoin expertise. Their Inheritance Boot Camp ($4,000 first year) provides four advisory meetings, estate gap analysis, account retitling support, and a trust vault subscription. Unchained also supports Transfer-on-Death beneficiary designations to bypass probate.

Casa includes inheritance on all paid plans. You designate a recipient within the app and share an encrypted mobile key via QR code. If you become incapacitated, the recipient initiates a transfer request that triggers a six-month waiting period. During this window, Casa notifies the vault owner. If no objection is raised, the recipient gains access. No death certificate or court order is required. Private Client members can opt for enhanced verification that eliminates the waiting period.

Nunchuk's Honey Badger plan uses on-chain timelocks for inheritance. You set a future date at which a designated beneficiary can sweep funds, and refresh the timelock periodically (typically annually) to keep funds locked. If you stop refreshing, the timelock expires and the wallet rules automatically change to allow the beneficiary to claim. Because the timelock is committed to the blockchain, the parameters are immutable once set: the plan executes exactly as configured regardless of whether Nunchuk is operational. Nunchuk also supports COLDCARD and TAPSIGNER as inheritance key hardware. Their Byzantine platform extends these features for advisors managing client custody.

Caravan and Sparrow provide no built-in inheritance features. DIY users must arrange their own key distribution, documentation, and legal frameworks.

Key Replacement and Recovery

Losing a hardware wallet is inevitable over a long enough time horizon. The key question is how each service handles the transition to a replacement device without creating a window of vulnerability.

Unchained's current recommended approach is to create a new vault with the replacement key rather than in-place key rotation. You set up the new device, create a new vault, transfer your subscription (with a 30-day grace period), and move funds via an internal transfer. If the old device is lost, you use your remaining key plus Unchained's co-sign to authorize the migration. Standard Bitcoin network fees apply for the on-chain transfer.

Casa handles key replacement (called "key rotation") within the app. You mark the old key for replacement, set up the new hardware device, and transfer funds to the new vault configuration. If the old key is lost, you request a Casa Recovery Key signature: this triggers a mandatory waiting period of seven days for 3-key vaults or 48 hours for 5-key vaults before the transfer can finalize. Premium members get one free device replacement per year. Casa also provides a Sovereign Recovery kit for recovering funds independently using open-source tools like Sparrow.

Nunchuk offers automated wallet rollover on paid plans. This feature handles the fund transfer from an old wallet configuration to a new one with a replacement key, reducing the risk of human error. The free tier requires manual key replacement by creating a new wallet and sweeping funds. Nunchuk's emergency lockdown feature lets you temporarily freeze a wallet if a key is stolen, buying time to arrange replacement.

With Caravan and Sparrow, key replacement is entirely manual. You create a new multisig wallet with the replacement key and sweep funds from the old address. This requires comfort with PSBT workflows and careful verification of the new wallet configuration.

What Happens If the Service Shuts Down

A critical advantage of collaborative custody over full third-party custody is that you always retain enough keys to access your funds independently. However, the ease of recovery varies.

Unchained users hold two of three keys. If Unchained disappears, those two keys are sufficient to sign transactions without any involvement from the company. Unchained built Caravan specifically as an open-source recovery tool for this scenario: clients can load their wallet configuration file into Caravan or Sparrow and spend directly from their vault. Unchained's stated philosophy is that "custody software should outlast companies."

Casa provides Sovereign Recovery instructions to every vault member at setup (and re-sends them on every key rotation). These instructions are also hosted on the third-party site walletsrecovery.org. In a 2-of-3 vault, you need your hardware key plus the mobile key seed to sign without Casa. In a 3-of-5 vault, you need any three of your keys. Recovery can be performed entirely through Sparrow or Electrum.

Nunchuk users on the free tier hold all keys themselves and face no dependency on Nunchuk at all. Paid plan users hold enough keys to meet the quorum without Nunchuk's platform key. Nunchuk's client apps are open-source (GPL-3.0), so the community could maintain the software independently. Wallets use BIP39 seed phrases and BIP129 wallet configuration files, making them recoverable in Sparrow or Electrum. For on-chain timelock inheritance plans, the timelock expires and executes regardless of whether Nunchuk exists.

Caravan and Sparrow are open-source software with no service dependency. Your keys, your coins: the software is simply a coordinator.

Mobile App and Platform Availability

Unchained offers iOS and Android companion apps for monitoring balances, approving transactions, and receiving notifications. However, all hardware wallet signing must be done on a desktop browser via USB: the mobile app does not support direct hardware wallet interaction. Vault creation and key setup happen through the web dashboard.

Casa is mobile-first. The Casa app is available on iOS and Android and serves as both a key manager (holding one mobile key) and the primary interface for vault operations, inheritance setup, and transaction signing. Desktop access via Chrome or Brave is available for hardware wallet operations.

Nunchuk offers native apps on iOS, Android, Windows, macOS, and Linux. The mobile apps support NFC signing with TAPSIGNER and Coldcard, while the desktop clients add USB support for Trezor, Ledger, and BitBox02. Encrypted cross-device sync keeps wallets consistent across platforms.

Caravan runs in any modern web browser with no installation required. Sparrow is a desktop application available for Windows, macOS, and Linux, with no mobile version.

Privacy Considerations

The amount of personal information required to use each service varies significantly. Unchained requires full KYC verification (name, date of birth, photo ID, address) because it operates as a financial institution under the Bank Secrecy Act. This is the tradeoff for accessing Unchained's additional financial services like Bitcoin IRAs and lending.

Casa does not require KYC for its self-custody plans. You can set up a vault with only an email address. Nunchuk takes privacy further: no personal data beyond an email, no KYC, and support for connecting through your own full node over Tor. Nunchuk has positioned itself as the no-KYC standard for assisted multisig.

Caravan and Sparrow collect no personal information whatsoever. Sparrow can connect to your own node or a public Electrum server, and supports Tor routing for network-level privacy.

How to Choose the Right Multisig Service

The right choice depends on where you fall on the spectrum between convenience and sovereignty:

• If you want a turnkey solution with financial services (IRA, lending, trading): Unchained provides the most integrated Bitcoin financial platform, at the cost of full KYC
• If you want mobile-first custody with multi-asset support: Casa offers the most polished app experience and supports BTC, ETH, USDC, and USDT
• If privacy is non-negotiable: Nunchuk requires no KYC, supports Tor, and offers on-chain timelock inheritance that works independently of the company
• If you want the lowest-cost assisted option: Nunchuk Iron Hand at $120/year is the most affordable managed multisig plan
• If you want maximum control at zero cost: Sparrow Wallet with your own hardware wallets gives you full sovereignty with no subscription and no third-party dependencies
• If you need a recovery tool for an existing multisig vault: Caravan is purpose-built for this and runs entirely in the browser

For users exploring the broader collaborative custody landscape, including newer entrants, see the collaborative custody comparison and multisig planner tool.

Frequently Asked Questions

What is the difference between multisig and MPC custody?

Multisig uses multiple independent private keys, each stored on its own device, and requires a threshold of those keys to sign a transaction on-chain. The signing policy is enforced by Bitcoin Script itself. MPC splits a single private key into shares distributed across parties, who jointly compute a signature without ever reconstructing the full key. Multisig is natively supported by Bitcoin and fully verifiable on-chain, while MPC relies on off-chain cryptographic protocols. For a detailed comparison, see our MPC vs multisig custody analysis.

Can I lose my Bitcoin if the multisig service company goes out of business?

No, assuming the service uses genuine collaborative custody. In a properly configured multisig vault, you hold enough keys to meet the spending quorum without the company's key. All three major managed services (Unchained, Casa, Nunchuk) are designed so that you can recover funds using open-source tools like Sparrow or Caravan even if the company ceases to exist. The critical step is verifying that you actually control enough keys at setup time.

Is multisig worth it for small Bitcoin holdings?

Multisig adds cost and complexity. If you hold a small amount, a single hardware wallet with a strong seed phrase backup may be sufficient. The common threshold where users consider multisig is when the value of their holdings exceeds the cost of the hardware and subscription by a meaningful margin. Nunchuk's free tier and Sparrow Wallet allow you to experiment with multisig at zero cost to decide if the workflow suits you before committing to a paid service.

How many hardware wallets do I need for multisig?

For a 2-of-3 setup with a managed service, you typically need two hardware wallets (you hold both keys, the service holds the third). For Casa's 2-of-3, one key lives on the mobile app and you need one hardware wallet. For a 3-of-5 setup like Casa Premium or Nunchuk Premier, you need multiple hardware wallets. For fully DIY multisig, you need one device per key in the quorum, and each device should be from a different manufacturer to avoid correlated firmware vulnerabilities.

Which multisig service has the best inheritance planning?

Each service takes a different approach. Nunchuk's on-chain timelock inheritance is the most trustless: once set, the plan executes on the pre-determined date regardless of whether Nunchuk exists. Casa's six-month waiting period with owner notification balances security against premature activation. Unchained's Inheritance Protocol provides the most comprehensive documentation and advisory support, especially through their Inheritance Boot Camp. The best choice depends on whether you prioritize cryptographic guarantees (Nunchuk), ease of use for non-technical heirs (Casa), or professional estate planning support (Unchained).

Do I need KYC to use a Bitcoin multisig wallet?

Not necessarily. Casa and Nunchuk do not require KYC for their custody plans. Nunchuk collects nothing beyond an email address. Unchained requires full KYC because it operates as a regulated financial institution offering services like IRAs and loans. Fully DIY options like Sparrow and Caravan require no identity information at all.

What is collaborative custody?

Collaborative custody is a multisig arrangement where a service provider holds one or more keys but never enough to unilaterally spend your funds. The provider assists with key management, recovery, and inheritance, while you retain sovereign control. This model sits between full self-custody (you hold all keys) and full third-party custody (an exchange holds everything). It eliminates the single point of failure inherent in both extremes.

This tool is for informational purposes only and does not constitute financial advice. Pricing, features, and supported hardware are based on publicly available information and may change. Always verify current details on each provider's website before making custody decisions.