Bitcoin Wallet SDK
The best platform to run bitcoin and stablecoin operations. One SDK for instant payments, self-custodial wallets, and native stablecoins.
Trusted by teams like Tether, Breez, and Xverse building on Spark
Bitcoin infrastructure wasn't built for modern wallets
On-chain transactions take 10+ minutes and cost unpredictable fees. Lightning requires running nodes, managing channels, provisioning inbound liquidity, and handling routing failures. Stablecoins don't exist natively on Bitcoin at all: they live on separate chains with separate infrastructure. If you want to offer all three in one wallet, you're stitching together three different stacks, each with its own failure modes, operational burden, and integration surface. Most teams spend months on plumbing before they can ship anything.
What we do
Everything your wallet needs, one integration
Instant Bitcoin deposits with 0-conf
Receive bitcoin without waiting for block confirmations. Spark's zero-confirmation deposits credit funds the moment a transaction is broadcast, so your users never stare at a pending screen.
Lightning without the infrastructure
Full Lightning Network interoperability with no nodes to run, no channels to open, no liquidity to manage, and no routing failures. Spark solved the hard parts: inbound capacity, rebalancing, and payment reliability are handled at the protocol layer.
Native stablecoins on Bitcoin
USDT and USDB live natively on Spark: same wallet, same SDK, same instant settlement. No bridges, no wrapped tokens, no separate chain. Your users hold real stablecoins alongside their bitcoin.
Self-custodial by default
Every wallet is backed by the user's own keys. No custodial risk on your side, no trust assumptions, no regulatory overhead from holding funds. You get the UX of a custodial app with the security model of self-custody.
Why Spark
The most complete Bitcoin infrastructure, behind one API
Instant settlement across all rails
Transactions on Spark settle in under a second. Lightning payments route without failures. On-chain deposits credit immediately with 0-conf. No more explaining confirmation times to users.
No nodes, no channels, no liquidity management
Traditional Lightning requires running infrastructure, provisioning liquidity, and handling channel management. Spark abstracts all of this away. You call an API, payments work.
Bitcoin and stablecoins in the same protocol
Other platforms force you to integrate separate chains for stablecoins. On Spark, BTC, USDT, and USDB share the same wallet, the same keys, and the same instant settlement.
Ship in days, scale without ops
The Spark SDK is available for mobile, web, and server environments. A few lines of code to initialize. No infrastructure to maintain as you grow: Spark handles the protocol layer.
Products
Instant Bitcoin Deposits
Receive on-chain bitcoin in seconds with 0-conf
Self-Custodial Lightning
Full Lightning send and receive, no nodes or channels
Bitcoin Buy and Sell
The cheapest way to buy and sell bitcoin directly to a self-custodial wallet
Bitcoin Rewards
Distribute bitcoin rewards and incentives at scale
Cross-Chain Bitcoin Swaps
The fastest, cheapest way to move bitcoin into stablecoins and other assets
Stablecoin Issuance
Issue and manage stablecoins natively on Bitcoin
Trusted by the world's best wallet teams.
From wallets to stablecoin issuers, the best teams ship on Spark.Spark and WDK unlock programmable, resilient Bitcoin over Lightning: instant global payments without compromising custody or privacy.
We care deeply about network effects. Issuing on Spark is a no-brainer for Brale, it has the potential to bring billions of people to stablecoins.
Our goal is to make Xverse the definitive home of BitcoinFi, and integrating Spark is a monumental step.
Spark is transformative. It redefines what Bitcoin can be, evolving it from a monetary network into an application platform.
We're excited to build on Spark to unlock powerful Bitcoin-based rails for all the users we serve without requiring them to be crypto-native.
Flashnet couldn't exist without Spark. It's the best infrastructure for building real money apps on Bitcoin, period.
FAQ
The Spark SDK is available for TypeScript (Node.js, browser, React Native). Breez also offers a Rust SDK with bindings for Swift, Kotlin, Python, Flutter, Go, C#, and WebAssembly.
That's up to you. Spark is self-custodial by default, but key management can be abstracted behind your app's UX. Users can back up with seed phrases, passkeys, or your own auth flow.
Spark credits on-chain bitcoin deposits instantly by validating the transaction at broadcast time. The protocol handles the confirmation risk so your users don't wait for blocks.
USDT (Tether) and USDB (issued by Brale via Flashnet) are live on Spark today. Both are native Bitcoin assets: no bridges, no wrapped tokens.
Transfers within Spark are fee-free. You only pay Bitcoin network fees when depositing to or withdrawing from Spark.
Yes. Spark is fully interoperable with Lightning: your users can send to and receive from any Lightning wallet. You can migrate incrementally without breaking existing payment flows.
Start building with Spark
Spark integrates into your app and handles the complexity that comes with Bitcoin, Lightning, and stablecoins.