Become the acquirer.
Not a hop to one.
A gateway forwards your REST call to someone else's acquirer. Payrithm composes the scheme message itself: a real Visa Base I, Mastercard BankNet, or Amex AEIPS ISO 8583 0100, or an ISO 20022 pacs.008, as the acquiring participant. One Stripe-shaped API to authorize, capture, void, and refund. Every call is composed and gated, fail-closed.
Pre-GA · taking design partners — see what runs today
a gateway hops your call to someone else's acquirer · Payrithm composes the message itself — Visa Base I · Mastercard BankNet · Amex AEIPS · ISO 20022 pacs.008 → one ledger
# Payrithm composes the Visa Base I 0100 itself. The BIN routes the rail.
curl -X POST https://api.stringio.io/v1/authorize \
-H "Authorization: Bearer sk_live_••••" \
-H "Idempotency-Key: a1f3-trip-1184" \
-d '{ "merchant_id":"mer_2a9f4b7c", "amount_minor":4200,
"currency":"USD", "pan":"4929••••••••1729", "capture":false }'
→ 201 { "status": "requires_capture", "rail": "visa_base_i", "stan": "048217" }
→ then capture 5000 against the 4200 authorization:
→ 422 { "error": "guard_violation", "detail": "capture exceeds authorized amount" }
fail-closed · refuses, never clamps
Card schemes
Visa Base I · MC BankNet · Amex AEIPS
Account-to-account
SEPA CT/DD · FedNow · TCH RTP
Brazil · Pix
pacs.008 over the SPI
…and the seam to the rest
the 21-rail enum is closed; composers wired rail-by-rail
Eight rails composed today: 8 / 21 wired. Within a wire-family, a new scheme is a DE-profile, not a new codec.
Three systems. Three sets of books.
Each does its job. But wherever these systems meet — across authorization, clearing and settlement — a reconciliation seam opens: the numbers get re-keyed, re-batched and re-timed, and can slip out of sight until the close.
three systems · a seam at every boundary
gateway · PSP · acquirer, composed on one ledger
StringIO collapses the gateway, the PSP and the acquirer into one line. Nothing hands off; nothing is separate — so there's no seam to reconcile across. Auth and settlement post to the same ledger, reconciled to the cent before the money moves. Three boxes hand the numbers back and forth. One line never does.
One page, every method
Cards, wallets, net banking, mobile recharge and more on one checkout. The buyer chooses and pays in a single view, never bounced across pages.
One endpoint, routed for you
A single API reaches every method. Payrithm routes each transaction to the right partner or rail behind one merchant experience.
API-first, or hosted
Build against the API for full control, or drop in the hosted checkout to go live fast. Same engine underneath either way.
New methods, no re-integration
New payment methods and drop-in commerce plugins turn on in the same integration as they reach the market. You ship once.
Own every authorization you accept.
A card tap becomes a real scheme authorization composed as the acquiring participant.