How Sandbox Works
Every new account starts in sandbox mode. Test keys (sk_test_*) activate sandbox behavior:
| Feature | Sandbox | Live |
|---|---|---|
| Cards | Fake card 4242 4242 4242 4242 | Real Modulr Visa card |
| Funding | Virtual balance (instant) | SEPA transfer to your IBAN |
| Checkout | Form is filled, no real charge | Real Visa transaction |
| Balance | Not deducted on checkout | Deducted from wallet |
| Policy Engine | Fully functional | Fully functional |
| Webhooks | Real HTTP calls | Real HTTP calls |
Test Cards
| Card | Number | Use Case |
|---|---|---|
| Success | 4242 4242 4242 4242 | Default — always succeeds |
| Decline | 4000 0000 0000 0002 | Simulates declined payment |
| Insufficient | 4000 0000 0000 9995 | Simulates insufficient funds |
- Expiry:
12/28 - CVV:
123
Going Live
When ready for real payments:- Go to Dashboard → Go Live
- Choose Individual or Business account
- Complete KYC verification (Modulr)
- Receive your own IBAN
- Fund via SEPA transfer
- Create live API key (
sk_live_*) - Your agents now use real Visa cards