Best B2B Fiat-to-Crypto Payment Gateway for Developers

A fiat-to-crypto gateway is a payment infrastructure layer that lets businesses convert traditional currencies into digital assets and transfer them directly within their product via an API. Think wallets, DeFi apps, commerce stores, or fintech platforms.

The two core functions are on-ramp, which brings fiat money into the crypto world, and off-ramp, which takes it back out. It's a bit like an airport currency exchange, except the conversion happens in the background and the user doesn't have to touch it.

It also handles compliance by design. KYC, AML, and transaction monitoring come built in, so product teams don't have to build that infrastructure from scratch. Business stablecoin payments grew 733% year over year in 2025, which gives a sense of where the market is heading, according to McKinsey and Artemis Analytics.

A typical transaction moves through these steps:

1. The user selects a crypto asset and amount, and the gateway renders a payment UI via a hosted widget, SDK, or direct API call.
2. Automated KYC and AML checks run in the background, returning users' clearances in seconds.
3. The user pays via card, Apple Pay, bank transfer (SEPA or ACH), or a local payment rail.
4. The gateway locks the exchange rate, typically for 15 to 30 seconds, and converts fiat to crypto.
5. The digital asset lands in the user's wallet; settlement time depends on the network (Solana ~1 second, Ethereum 12-15 seconds, Bitcoin up to 60 minutes).

These are the criteria that tend to matter most when evaluating a provider for a B2B integration.

• API quality and sandbox access. Well-documented REST APIs, mobile and web SDKs, webhook support, and a sandbox environment for pre-production testing. Without sandbox access, there's no safe way to validate the integration before it touches real money.

• Built-in KYC and AML. The gateway should handle identity verification, sanctions screening, and AML checks natively. Modern vendors clear returning users in seconds, which keeps onboarding from becoming a drop-off point.

• Payment method coverage. Local rail support (SEPA, ACH, PIX, UPI) is what determines which markets the product can serve. Cards are the baseline; regional rails are where gaps tend to appear.

• Geographic reach and licensing. Verify that the provider holds regulatory approvals in the specific jurisdictions where users transact. A headline country count without confirmed licensing means very little.

• Supported assets and chains. BTC, ETH, USDT, and USDC are the baselines. Products targeting broader audiences need access to long-tail tokens, meaning fewer mainstream assets beyond the top 10, and multi-chain settlement.

• Fee structure transparency. Card processing typically runs 2–5%, with an FX spread of 0.5–2% on top. Bundled pricing makes volume-based cost comparisons nearly impossible.

• Compliance tooling. Illicit crypto volume hit a record of $158 billion in 2025, up 145% from the year before, according to TRM Labs. A gateway with weak transaction monitoring carries that exposure. Weak transaction monitoring carries that exposure directly onto the product.

The right fit depends on where the product operates, who it serves, and how much of the compliance stack the team wants to own.

Mercuryo is a payments infrastructure platform covering 150+ countries with local currency support, including Turkish Lira, Nigerian Naira, Mexican Peso, and Brazilian Real. Integration options include an iFrame widget, a full API for custom payment flows, and SDK support for web and mobile.

Payment methods span bank cards, SEPA, bank transfers, Apple Pay, Google Pay, and local rails, with PCI DSS certification included. In December 2025, Mercuryo announced a partnership with Coinme to expand compliant fiat-to-crypto access across 48 U.S. states.

Best for: DeFi platforms, Web3 wallets, and SaaS apps that need a white-label on/off-ramp with enterprise compliance depth.

MoonPay operates in 160+ countries with headless Apple Pay, Google Pay, and card payments, meaning the checkout renders directly on the developer's own domain with no redirects. Fees in Europe run 0%–4.5% depending on partner tier, with a minimum of €3.99 on smaller transactions. Partners can layer an additional ecosystem fee of up to 2%.

Best for: NFT platforms, Web3 wallets, and consumer-facing apps in developed markets.

Transak covers 150+ countries with a developer-first SDK that supports both widget and full API integration paths. Its strength is the depth of local payment methods in Asia, Africa, and Latin America. Fees typically run 1%–2% plus spread, which makes it competitive for volume-heavy integrations.

Best for: Global platforms with diverse user bases in emerging markets, gaming apps, and DeFi protocols.

Ramp supports 80+ blockchains and 40+ fiat currencies across 150+ countries. Its architecture lets developers route on-ramp flows directly into smart contracts, which suits DEX front-ends and yield protocols well.

Best for: DeFi protocols, DEX front-ends, and Web3 wallets that need a multi-chain on-ramp.

Banxa targets large exchanges and institutional platforms, operating in 120+ countries with both card and bank transfer support. Fees generally run 2%–3%, with volume-based pricing available for partners at higher transaction tiers.

Best for: Crypto exchanges, trading platforms, and fintechs with compliance-first requirements.

Onramper is an aggregator that connects 25+ on-ramp providers through a single API, giving access to 175+ payment methods with smart routing logic. Teams get broader geographic coverage and higher approval rates without managing multiple vendor relationships.

Best for: Teams with limited resources, MVPs, and platforms serving highly fragmented geographic markets.

Beyond the comparison table, four factors tend to determine whether a gateway works in practice.

Pressure-test these before signing:

1. Regulatory coverage. Confirm the provider holds licenses in every jurisdiction where users transact. Brands such as Mercuryo publishes its full list at mercuryo.io/legal/licenses.
2. Approval rates by region. Ask vendors directly. This number has a direct impact on revenue.
3. Settlement model. Some gateways settle in crypto to a wallet; others offer fiat payouts. Misalignment here creates real operational friction.
4. Fee structure at volume. Published rates are the ceiling. Most enterprise options offer custom pricing above certain monthly thresholds.

Fiat-to-crypto infrastructure has matured enough that the technical barrier is no longer the hard part. Most teams start with a widget to validate the flow, then move to a full API once the use case is proven. The options in this guide cover most combinations of geography, compliance tier, and integration depth.

A crypto payment gateway lets merchants accept cryptocurrency from users who already hold it. A fiat-to-crypto gateway goes further and converts traditional currency into digital assets during the transaction, so the user doesn't need to own crypto beforehand. For B2B products onboarding Web2 users, the fiat-to-crypto layer is what makes adoption possible.

Card processing fees typically run 1%–5.5% depending on the provider and transaction size, with an FX spread of 0.5%–2% on top. Most enterprise providers offer custom pricing above certain monthly volumes.

Yes, most enterprise-grade providers handle KYC, AML screening, and sanctions check natively. Some run automated identity verification that clears returning users in seconds, while others offer tiered KYC flows tied to transaction volume thresholds. Confirming what the gateway covers and what it doesn't before integration is worth doing.