What Is a WaaS API?
What is a WaaS API? It is the programming interface that Wallet-as-a-Service (WaaS) exposes for a business’s systems to call. Through it, a business’s backend creates wallets and addresses, initiates transfers, checks balances, and receives deposit and transaction status notifications via webhooks. Key management, signing, and on-chain interactions all happen behind the API, so the engineering team only has to handle business logic.
What Endpoints Does a WaaS API Usually Include?
The first category is wallet and address endpoints, used to create wallet accounts, generate addresses in bulk for users or merchants, and check balances for each address on each chain. The second is transaction endpoints, used to initiate transfers, estimate fees, and check transaction status, with some providers also supporting contract calls and message signing.
The third category is callback endpoints (webhooks). When an address receives a deposit, a transaction is confirmed, or an approval status changes, WaaS notifies the business’s server proactively, so the business doesn’t have to keep polling. The fourth is risk and compliance endpoints, used to manage whitelists, configure transaction policies, and retrieve anti-money laundering screening results.
Different use cases emphasize different endpoints: exchanges rely most on address generation, deposit callbacks, and sweeping, while payment companies focus more on stablecoin transfers and reconciliation. For the key API considerations in stablecoin payments, see Wallet API for Stablecoin Payments: The Technical Checklist Most Teams Skip.
How Does a WaaS API Keep Calls Secure?
Because the API can initiate transfers directly, its security design matters as much as the private keys. A common approach is to identify the caller with an API key, sign each request asymmetrically, add timestamps to prevent replay attacks, and allow calls only from whitelisted IPs.
Webhooks need verification too. When the business receives a callback, it should first verify the WaaS signature to confirm the notification really came from the provider before crediting the user; otherwise, attackers could forge deposit notifications. More importantly, risk rules should be enforced on the WaaS server side: even if an API key is stolen, transfers to addresses outside the whitelist are blocked. For more on the risks, see Is Wallet-as-a-Service Secure?
What Are the Steps to Integrate a WaaS API?
The first step is to open an account and a test environment, generate API keys, and configure the IP whitelist and callback URL. The second is to run the core flows end to end on testnet: generating addresses, receiving deposit callbacks, initiating withdrawals, and handling approvals and failed retries. The third is to configure risk rules and approvers and connect reconciliation with internal ledger systems. Finally, switch to mainnet and start with a limited rollout using small amounts.
Two areas cause the most problems. The first is idempotent callback handling: the same deposit may trigger multiple notifications, so you must deduplicate by transaction hash to avoid crediting twice. The second is on-chain confirmations and reorganizations: set a sensible number of confirmations for each chain. If things go smoothly, the whole integration usually takes just a few weeks, far faster than building a wallet in-house.
Conclusion
What is a WaaS API? It is the interface businesses use to call Wallet-as-a-Service, covering four types of functions: address management, transactions, callbacks, and risk and compliance. When integrating, manage API keys and request signing carefully, verify every callback, and thoroughly test idempotency and reconciliation logic on testnet, and you can go live securely within a few weeks.
Want to see how a WaaS API fits into your systems? Explore Safeheron WaaS, or contact the Safeheron sales team to book a one-on-one demo
