The short answer
A payment gateway is the software that sits on your checkout page, tokenizes card data, and sends authorization requests out of your environment and into the payments ecosystem. A payment processor (often called an acquirer or merchant services provider) is the bank-adjacent entity that actually submits those authorizations to the card networks, receives settlement funds, and deposits them into your merchant bank account. Two different jobs, two different companies, often two different contracts.
The flow in four steps
- Customer enters card at checkout. The gateway captures the data via JavaScript or API, tokenizes it, and sends an authorization request.
- Gateway routes to processor. The gateway's software knows which processor is assigned to your account and forwards the request.
- Processor requests auth from the network. The processor submits to Visa/Mastercard/Amex, which forward to the issuing bank.
- Authorization flows back. Approved or declined, the answer returns through the processor, through the gateway, to your checkout UI.
Why the split exists
Gateways compete on developer experience, feature depth (vaulting, recurring, 3DS, fraud filters), and integration breadth. Processors compete on banking relationships, interchange access, risk underwriting, and pricing. Separating the two lets you pick the best of each and swap one without re-integrating the other.
Bundled vs unbundled
- Bundled (Stripe, Square, PayPal, Adyen): The same company is both gateway and processor. Fast integration. Single support contract. Less flexibility — you can't swap the processor without leaving the gateway.
- Unbundled (NMI + Easy Pay Direct, Authorize.Net + Elavon, USAePay + Durango): Two companies. You integrate once with the gateway and can swap the processor underneath without changing your checkout code. This is the standard architecture for high-risk and multi-MID portfolios.
What operators need to know
- When a transaction fails, you need to know which side broke. "Gateway timeout" vs. "processor decline" are different problems with different fixes. Your logs should label both.
- Gateway fees and processor fees are separate line items. Gateway: $25-$50/mo plus $0.05-$0.10 per transaction. Processor: interchange + assessments + markup. Your statement should show both.
- You can change processors without changing gateways. If your gateway is NMI, you can swap acquirers by updating a single merchant-ID configuration. No checkout re-integration needed. This is the multi-MID routing advantage.
- You can't always change gateways without changing processors. Bundled providers (Stripe) make switching gateway-only impossible — leaving the gateway means leaving the processor.
- Multi-brand operators should prefer unbundled architecture. One gateway (for checkout consistency) routing to multiple processors (for volume distribution, reserve management, and failover) is the standard multiflow deployment pattern.
Real-world combos
- Stripe checkout → Stripe processing (bundled).
- Shopify checkout → Stripe or Authorize.Net processing (Shopify is the gateway + storefront, you choose processor).
- NMI gateway → Easy Pay Direct + Durango + PaymentCloud (unbundled, multi-MID high-risk).
- Braintree gateway → Braintree processing (bundled, but can be swapped for Adyen or others via Braintree's multi-processor API).
See also payment gateway, payment processor, and high-risk payment gateway.