Bitcoin Custody API Comparison: Developer Platforms

Custody API Platforms Overview

Developers building institutional Bitcoin products need a custody API that handles key management, transaction signing, and policy enforcement without exposing raw private keys. The four major providers in this space each take a different approach to these problems: Fireblocks and Copper use multi-party computation (MPC), BitGo supports both multisig and MPC, and Anchorage Digital relies on hardware security modules (HSMs).

The choice of custody provider affects everything from transaction latency and fee optimization to regulatory compliance and insurance coverage. This comparison focuses on what matters to developers integrating these APIs: SDK quality, signing models, PSBT support, Taproot compatibility, and policy engine flexibility.

For a broader look at custody solutions beyond API-first platforms, see our institutional custody comparison and Bitcoin multisig setup guide.

Key Management Models

The key management architecture determines how signing authority is distributed, how transactions are authorized, and what happens if a single party is compromised. Each model has distinct tradeoffs for security, performance, and Bitcoin-native compatibility.

MPC (Fireblocks, Copper)

Fireblocks uses MPC-CMP (Collaborative Multi-Party), distributing three key shares across the client, Fireblocks, and a third party (an automated API co-signer for hot wallets, a mobile device for warm wallets, or an air-gapped device for cold wallets). The private key is never assembled in one location. Copper follows a similar 2-of-3 MPC quorum where key shards are held by the client, Copper, and a nominated third party.

MPC transactions appear as standard single-signature transactions on-chain, which provides privacy advantages and lower fees compared to multisig. The tradeoff is vendor lock-in to proprietary cryptographic implementations: migrating away from an MPC provider requires a coordinated key resharing ceremony rather than a simple key export. For a deeper technical analysis, see our research on MPC vs multisig custody models.

Multisig + MPC (BitGo)

BitGo is unique in offering both traditional 2-of-3 multisignature (native Bitcoin P2SH-P2WSH) and MPC-based threshold signatures (TSS). With multisig, three independent keys are generated: the user key, a BitGo key, and a backup key. Any two of three are required to sign. The authorization rules are enforced on-chain by Bitcoin Script, making them auditable by anyone.

BitGo's MPC/TSS option works similarly to Fireblocks: key shares are generated independently across parties and the private key never exists in complete form. This gives developers the flexibility to choose on-chain verifiability (multisig) or off-chain privacy and lower fees (MPC) depending on the use case.

HSM (Anchorage Digital)

Anchorage takes a hardware-first approach, generating and storing keys inside FIPS 140-2 validated HSMs. Key generation occurs in an air-gapped environment, and transaction authorization requires biometric quorum approval from multiple authorized operators. This model is familiar to traditional finance institutions and aligns closely with banking security standards.

The tradeoff is flexibility: HSM-centric signing can constrain high-velocity automated workflows compared to MPC, and the hardware dependency introduces operational complexity for disaster recovery and geographic distribution.

Transaction Policy Engines

Policy engines govern which transactions are automatically approved, which require human review, and which are blocked entirely. For developers, the depth of the policy API determines how much business logic can be encoded at the custody layer versus the application layer.

Fireblocks' Transaction Authorization Policy (TAP) is the most developer-friendly: rules are processed top-down, and the full policy lifecycle (create, update, simulate) is available via the API. BitGo provides a solid balance of API access and dashboard configuration. Anchorage's policies are tightly integrated with its banking compliance framework but are less programmable. Copper's Zero-Trust methodology enforces consensus requirements, though detailed policy customization is not well documented publicly.

Bitcoin-Native Feature Support

For developers building Bitcoin-specific products, support for native transaction formats matters. PSBT (BIP-174) enables interoperable transaction construction across wallets and signing devices. Taproot (BIP-341) unlocks Schnorr signatures, lower fees for complex spending conditions, and improved privacy through key-path spends.

BitGo stands out as the only provider with publicly documented support for the full suite of Bitcoin-native features: PSBT workflows, Taproot addresses (P2TR), MuSig2 for efficient multi-party signing, RBF and CPFP for fee bumping, and granular UTXO management including consolidation, reservation, and freezing. The other three providers abstract Bitcoin signing behind their custody layers, which may support these features internally but do not expose them in public API documentation.

If your application requires direct interaction with Bitcoin transaction primitives (for example, constructing PSBTs for hardware wallet co-signing or building Taproot Assets workflows), BitGo's API provides the necessary low-level control. MPC-based providers like Fireblocks and Copper prioritize a chain-agnostic abstraction that simplifies multi-chain support at the cost of Bitcoin-specific programmability.

Regulatory Licenses and Compliance

Regulatory status directly affects whether a provider can serve as a qualified custodian under SEC rules. As of mid-2026, the OCC has expanded digital asset bank charters significantly, but the landscape remains complex.

• Fireblocks operates Fireblocks Trust Company, LLC, a limited-purpose trust company chartered by the NYDFS. SOC 2 Type II audited by Ernst & Young with zero material findings. Also holds SOC 1, ISO 27001, 27017, 27018, and CCSS-QSP Level 3 certifications.
• BitGo holds an OCC-chartered national trust bank (BitGo Bank & Trust, N.A.) and a separate NYDFS-regulated trust company. Licensed as a Major Payment Institution in Singapore (MAS), VARA-licensed in the UAE, and MiCAR-authorized via BaFin in Germany. SOC 2 Type II certified since 2019.
• Anchorage Digital Bank N.A. became the first federally chartered crypto-native bank in January 2021 (OCC). It operates as a Federal Reserve member with full fiduciary powers. SOC 1 and SOC 2 Type II audited by Ernst & Young.
• Copper is registered in Switzerland as Copper Markets (Switzerland) AG. SOC 2 Type II certified. It does not hold an active custody license in the US or UK as of 2026, which limits its availability for US-regulated institutional clients.

For developers integrating custody into a regulated product, BitGo and Anchorage offer the broadest compliance coverage. BitGo has the most jurisdictions covered (US, Singapore, UAE, Germany, Denmark, Switzerland), while Anchorage has the deepest US federal regulatory standing through its national bank charter.

Insurance Coverage

Insurance limits vary by an order of magnitude across providers. Copper's $500M bespoke Crypto Crime policy (placed at Lloyd's of London) is the highest published figure in the industry. BitGo's $250M policy, also underwritten by Lloyd's syndicates, covers theft and operational failures for assets in qualified custody. Anchorage's coverage exceeds $350M across the full custodial lifecycle. Fireblocks provides $30M default coverage against hardware and software faults, with options to increase.

Note that insurance terms, exclusions, and claim pathways differ significantly between providers. Published limits represent maximum coverage, not per-client guarantees. No provider offers FDIC or SIPC insurance. For more on custody insurance, see our custody insurance comparison.

Pricing Models

None of the major custody API providers publish fully transparent pricing. All require direct sales engagement for enterprise contracts. Based on publicly available information:

• Fireblocks uses tiered subscription plans (Starter, Growth, Enterprise, Network). Starter plans reportedly begin around $699/month. Enterprise pricing reaches six figures annually.
• BitGo charges assets-under-custody (AUC) fees. Published examples show 0.25% on the first $1M in holdings per asset, declining at higher tiers. Transaction and premium feature fees apply separately.
• Anchorage charges AUC-based annual basis points, calculated monthly. Sample tiers start at 30 bps below $10M AUC, declining to 15 bps at $500M+. A $3,000/month minimum applies.
• Copper does not publish pricing. Enterprise-focused contracts require direct negotiation.

Choosing the Right Custody API

If your application requires deep Bitcoin transaction control (PSBT construction, Taproot support, UTXO management, fee bumping): BitGo is the strongest choice. Its dual multisig/MPC model and publicly documented Bitcoin-native features give developers the most flexibility for Bitcoin-specific products.

If you are building a multi-chain product and need a chain-agnostic abstraction with a programmable policy engine: Fireblocks offers the most developer-friendly API with the broadest blockchain coverage (150+ networks). Its TAP engine provides full API-driven policy automation.

If US federal regulatory compliance is the primary concern: Anchorage Digital's OCC national bank charter provides the deepest regulatory standing. The tradeoff is a smaller asset universe (~60 assets) and less publicly documented API surface.

If off-exchange settlement is a core workflow: Copper's ClearLoop network enables instant delegation to centralized exchanges while assets remain in MPC-secured custody, eliminating exchange counterparty risk. However, the lack of US/UK custody licenses limits its regulated footprint.

Developers building on Bitcoin layer 2 networks should also evaluate whether their custody provider supports the specific L2's signing requirements. For applications built on Spark, the custody layer must support the underlying Bitcoin key management that Spark's protocol depends on.

What Happened to Qredo?

Qredo, which offered decentralized MPC custody, entered UK administration in February 2024. Its assets were acquired by Fusion Laboratories Ltd, a new entity backed by 10T Holdings and 1RoundTable Partners. The platform was rebranded as Fusionchain, built on the Cosmos ecosystem, with a focus on self-custody and MPC node technology. Qredo is no longer a competitive institutional custody API provider in the same category as the platforms compared above.

Separately, Taurus Group (a Swiss custody and tokenization firm) has been expanding into institutional custody with partnerships including State Street and Santander. Taurus opened its first US office in October 2025 and holds FINMA approval. It is a distinct company from Qredo/Fusionchain and is worth watching as an emerging competitor.

Frequently Asked Questions

What is the difference between MPC and multisig for Bitcoin custody?

MPC distributes key shares across multiple parties so the private key is never assembled in one place. The resulting transaction appears as a standard single-sig transaction on-chain, providing privacy and lower fees. Multisig uses multiple independent keys with on-chain spending conditions enforced by Bitcoin Script. Multisig is auditable by anyone but costs more in transaction fees and reveals the threshold structure on-chain. BitGo supports both models, giving developers a choice based on their requirements.

Which custody API supports PSBT and Taproot?

Among the major providers, only BitGo has publicly documented support for PSBT (BIP-174), Taproot (BIP-341) addresses, and MuSig2 for efficient multi-party signing. Fireblocks, Anchorage, and Copper abstract Bitcoin signing behind their custody layers and do not publicly document support for these Bitcoin-native transaction formats. If your application requires direct PSBT construction or Taproot spend paths, verify support with each provider before committing.

What is a qualified custodian for crypto assets?

A qualified custodian is an entity that meets the SEC's custody rule requirements for safeguarding client assets. In the US, this includes national banks, state-chartered trust companies, and certain broker-dealers. Anchorage Digital (OCC national bank), BitGo (OCC national trust bank and NYDFS trust), and Fireblocks (NYDFS trust company) each qualify under different regulatory frameworks. Copper does not currently hold a US or UK custody license.

How much does institutional Bitcoin custody cost?

Pricing varies significantly by provider and scale. Fireblocks offers subscription tiers starting around $699/month for small deployments, with enterprise contracts reaching six figures annually. BitGo and Anchorage charge assets-under-custody (AUC) fees, typically ranging from 15 to 30 basis points annually depending on volume. All providers require direct sales engagement for precise quotes. Transaction fees, premium features, and compliance services are typically priced separately.

Can I use a custody API for Bitcoin layer 2 applications?

Yes, but compatibility depends on the specific L2 and the custody provider's signing capabilities. Most custody APIs support standard Bitcoin key management, which provides the foundation for L2 protocols that derive security from Bitcoin's base layer. For applications built on Bitcoin L2s like Spark, the custody provider needs to support the underlying Bitcoin signing operations. Evaluate each provider's documentation for support of the specific transaction types your L2 requires.

What insurance do Bitcoin custody APIs provide?

Published insurance limits range from $30M (Fireblocks) to $500M (Copper), with BitGo at $250M and Anchorage above $350M. Coverage typically protects against theft due to security breaches and operational failures. No crypto custody provider offers FDIC or SIPC insurance. Actual per-client coverage, exclusions, and claim processes vary by contract: published maximums represent total policy limits, not individual client guarantees. Always review the specific insurance terms in your custody agreement.

Is Fireblocks a custodian or a technology provider?

Both. Fireblocks historically operated primarily as a technology and infrastructure provider, offering its MPC platform for other institutions to build on. It now also operates Fireblocks Trust Company, LLC, a limited-purpose trust company chartered by the NYDFS, which enables it to serve as a qualified custodian directly. This dual role means developers can use Fireblocks either as a self-custody infrastructure layer or as a regulated custodial service.

This tool is for informational purposes only and does not constitute financial advice. Data is approximate and based on publicly available information as of mid-2026. Insurance limits, regulatory statuses, pricing, and feature support change frequently. Always verify current capabilities directly with each provider before making custody decisions.