Testnet Sandbox

The Blink sandbox is a fully separate environment that runs on testnet. It has its own API, hosted flow, and merchant registry, and settles deposits on Base Sepolia and Sepolia instead of mainnet. Use it when you want to develop without real funds — for example during a hackathon or early prototyping.

Mainnet remains the recommended way to verify your integration. The sandbox runs on test networks with test liquidity, so it cannot prove production readiness. Before going live, complete the Testing flow with a small real deposit and work through the Production Checklist.

Sandbox endpoints

Surface	Production	Sandbox
API	`https://api.blink.cash`	`https://api-sandbox.blink.cash`
Hosted flow	`https://pay.blink.cash`	`https://pay-sandbox.blink.cash`

Sandbox and production share nothing: merchants, keys, and transfers in one environment do not exist in the other.

Enable sandbox mode in the SDK

Pass environment: 'sandbox' when constructing the SDK. This points the hosted flow at https://pay-sandbox.blink.cash. An explicit webviewBaseUrl always takes precedence over environment.

import { Deposit } from '@swype-org/deposit';

const deposit = new Deposit({
  signer: '/api/sign-payment',
  environment: 'sandbox',
});

import { MobileDeposit } from '@swype-org/deposit-mobile';

const deposit = new MobileDeposit({
  signer: 'https://api.yourapp.com/sign-payment',
  callbackScheme: 'myapp',
  environment: 'sandbox',
  openUrl: (url) => WebBrowser.openBrowserAsync(url),
});

Register a sandbox merchant

Sandbox merchants are registered with the same flow as production, but against the sandbox API. Generate a key pair following Key Generation — use a dedicated key pair for sandbox, never your production key — and submit it to:

curl -X POST "https://api-sandbox.blink.cash/v1/merchants/applications" \
  -H "Content-Type: application/json" \
  -d '{
    "email": "dev@yourapp.com",
    "domain": "yourapp.com",
    "publicKey": "-----BEGIN PUBLIC KEY-----\n...\n-----END PUBLIC KEY-----\n",
    "description": "Testing our Blink integration on the sandbox before going live."
  }'

Sandbox applications are approved automatically — the returned merchantId is active immediately, so you can wire it into your signer and start depositing right away.

Supported testnets

Chain	Chain ID	Supported tokens
Base Sepolia	`84532`	`USDC`, `ETH`
Sepolia	`11155111`	`USDC`, `ETH`

Support differs by deposit method:

One-tap deposits (connected wallet): Base Sepolia and Sepolia only. Cross-chain routing between the two works — for example, depositing Sepolia USDC to a Base Sepolia destination.
Manual transfers (send from an exchange or wallet): same-chain deposits only, on Base Sepolia and Sepolia. Cross-chain manual transfers are not supported on testnet.

There is no testnet USDT. Tether does not maintain official testnet deployments, so USDC stands in for all stablecoin flows in the sandbox — the integration surface is identical, and switching to mainnet USDT is a config change.

Sandbox deposits are significantly slower than mainnet. Testnet routing depends on test-network block times and solver liquidity, so expect completion times well beyond what you will see in production.

Fund a test wallet

Testnet USDC — Circle’s testnet faucet supports both Base Sepolia and Sepolia.
Gas (ETH) — use the Google Cloud faucet for Sepolia or the Coinbase faucet for Base Sepolia.

Differences from production

	Production	Sandbox
Networks	60+ mainnets	Base Sepolia, Sepolia
Funds	Real	Testnet (faucet)
Merchant approval	Reviewed by Blink	Automatic
One-tap deposits	All supported source chains, cross-chain	Base Sepolia and Sepolia, cross-chain
Manual transfers	Cross-chain and same-chain	Same-chain only
Speed	Seconds	Significantly slower
USDT	Supported	Not available — use USDC

Getting Started

Integration Guide

Testnet Sandbox

Sandbox endpoints

Enable sandbox mode in the SDK

Register a sandbox merchant

Supported testnets

Fund a test wallet

Differences from production

​Sandbox endpoints

​Enable sandbox mode in the SDK

​Register a sandbox merchant

​Supported testnets

​Fund a test wallet

​Differences from production

Sandbox endpoints

Enable sandbox mode in the SDK

Register a sandbox merchant

Supported testnets

Fund a test wallet

Differences from production