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The 9 Best Payment Gateway & Credit Card APIs For Developers

When you're ready to dive into the world of credit card APIs, you'll want to compare and contrast the developer tools provided by payment services providers.

    Chris Motola
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Payment API

If you do a lot of your selling online, you’ve probably run up against some of the limitations that come with using a prefabricated payment setup. The good news is that you can configure your payment processing infrastructure. If you’re a developer or have access to developers, you can use a payment API to create a custom credit card processing setup — assuming you work with the right payment services provider or gateway.

When you’re ready to dive into the world of payment processing APIs, you’ll want to compare and contrast the developer tools provided by payment services providers. It’s important to evaluate them not only by the strength of their API but also by considering more mundane factors, such as how much they cost, the types of transactions they support, and how secure they are.

Learn More About Our Top Picks

CompanySummaryNext StepsSummary

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  • Subscription-based pricing
  • Quick access to API sandbox
  • Subscription-based pricing
  • Quick access to API sandbox

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  • Versatile toolset
  • Good documentation
  • Versatile toolset
  • Good documentation

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  • Top-tier developer support
  • Strong developer community
  • Top-tier developer support
  • Strong developer community

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  • Strong developer support
  • Unique payments platform
  • Strong developer support
  • Unique payments platform

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  • Excellent merchant services
  • Test server available
  • Excellent merchant services
  • Test server available

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Other Featured Options:

  • Braintree Payment Solutions:
    • Exhaustive developer resources
    • Can access PayPal's ecosystem
  • Adyen:
    • Strong international support
    • Easy-to-parse documentation
  • Authorize.Net:
    • Versatile payment gateway
    • Excellent dev tools with live console
  • Helcim:
    • International payments with interchange-plus pricing
    • Good developer tools

Read more below to learn why we chose these options.

What Can You Do With A Payment API?

An application programming interface (API) provides a set of functions external programmers can use to access and utilize a system. For example, if you were trying to pull information from Twitter into your app, you’d make calls to the Twitter API from within your app.

Payment APIs operate on the same principle. They allow you to access the functionality of the payment API within your own customized infrastructure. This way, you don’t have to build a payment processing infrastructure from the ground up, and you also don’t have to accept the limited configurations the payment processor offers out of the box.

Here are some examples of what you can do with a payment API:

  • Accept credit and debit card payments
  • Accept additional types of payments (such as ACH)
  • Set up recurring payments
  • Customize fields in the checkout
  • Bank transfers
  • Handle cryptocurrency
  • Route payments to different accounts using specified criteria
  • Customize security features

9 Best Credit Card & Payment APIs For Developers

When you’re evaluating a payment API, the first thing to remember is that it will be attached to a payment processing service. If you don’t care for the service’s rates or way of doing business, no amount of code will fix that. Here are our top API picks, including Stax by Fattmerchant, Square, Stripe Payments, and more.

1. Stax By Fattmerchant

Stax by Fattmerchant



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Pros

  • Transparent membership pricing
  • No long-term contract
  • Stax Pay integrated payments processing platform
  • Public documentation

Cons

  • Not suitable for low-volume businesses
  • Some billing issues reported

Stax by Fattmerchant is a merchant account provider and one that Merchant Maverick has rated very highly. That’s because it offers subscription-based pricing, which eliminates the percentage markup over interchange rates that you’re typically charged when you swipe a credit card. You’ll still have to pay the interchange fees, which your merchant account provider can’t do anything about, but if you’re looking for predictable, volume-friendly pricing, you can’t do much better.

The Stax API provides SDKs for Javascript and Python, though the RESTful API can be used with any language that can make API calls. One of the best things about Stax’s approach is how quickly you can set up an API sandbox to test out its features. You’ll be able to work payment processing into your existing software without having to worry about PCI compliance. The Omni Mobile SDK supports Android and iOS development, allowing you to add tokenized payment methods to your apps.

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2. Square

Square



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Pros

  • Predictable flat-rate pricing
  • No long-term contract
  • Enables omnichannel selling
  • Public documentation

Cons

  • Account stability issues
  • Not suitable for high-risk industries

Like Stripe, Square is a “full-stack” payment service that combines third-party processing with gateway functionality. But where Stripe is more focused on international and eCommerce support, Square has built up an enormous platform that provides a variety of tools to both eCommerce and brick-and-mortar businesses — including marketing, loans, loyalty programs, productivity, inventory, etc. — on top of processing card transactions. Of course, as a third-party processor, similar warnings apply regarding account stability and restrictions on the types of businesses Square will work with.

As you may expect of an ecosystem as large and complex as Square’s, several different Square APIs allow developers to access different parts of the processor’s infrastructure. Thankfully, Square provides an API Explorer to help you find what you need. Square provides ample documentation on its developer site, custom SDKs, and a sandbox to make development easier.

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3. Stripe Payments

Stripe Payments



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Pros

  • Predictable flat-rate pricing
  • No long-term contract
  • Excellent developer resources
  • Multicurrency support

Cons

  • Account stability issues
  • Not suitable for high-risk industries

Stripe Payments bills itself as a full-stack payment processor. That means it combines the functionality of a third-party payment processor and a gateway into a single package. This will be convenient for many businesses provided they don’t already have a merchant account that they want to hold onto, as Stripe doesn’t let you use its gateway à la carte; it’s all or nothing. Like other third-party processors, Stripe makes it easy for newer businesses to start accepting payments but at the cost of stability issues and industry restrictions.

When it comes to developer support, Stripe is pretty close to the gold standard for payment processors. The online documentation is exhaustive, easy to parse, and full of readily accessible code snippets in each of the server-side languages it supports (Ruby, Python, Java, PHP, Node.js, Go, and .NET). Stripe also has links to boilerplate projects you can clone and build upon. If there’s a chink in its armor, it’s that Stripe doesn’t provide a sandbox per se, although it does provide faux credit card numbers that you can use to test out your code.

While Stripe has generally been focused on eCommerce, developers may want to test out Stripe Terminal for POS transactions.

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4. Dwolla

Dwolla



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Pros

  • ACH and peer-to-peer transfer support
  • Excellent developer resources
  • Pay-as-you-go plan available

Cons

  • Can be expensive
  • No credit or debit card support

And now for something a little different. Dwolla isn’t a merchant account provider or a third-party processor. In fact, it’s not a service that processes credit card transactions at all. What Dwolla does offer is a way to facilitate ACH payments between two parties with minimal hassle. It also allows for additional peer-to-peer and bank transfers with its more expensive plans.

For developers, Dwolla offers a sandbox environment that is a complete replica of its production environment, providing a low-risk way to learn the ins and outs of the platform. The company’s online documentation is pretty deep, offering guides and references, as well as tools and SDKs (a helper library, for example). If you’re interested, you can even apply to be in Dwolla’s Integration Partner Program; just be aware that this requires you to follow Dwolla’s guidelines and best practices.

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5. PayJunction

PayJunction



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Pros

  • Transparent interchange-plus pricing
  • Good developer resources
  • eCheck processing available

Cons

  • Monthly fee for lower volume merchants
  • Not suitable for high-risk industries

PayJunction is another one-stop-shop payment service that combines a merchant account with its own proprietary payment gateway. PayJunction allows you to accept card and check payments in-store or remotely, and its system stores electronic signatures, eliminating the need to save signed receipts. Similar to Square, it removes the need for a traditional POS terminal, allowing you to process payments with iOS devices, although it also offers a “smart terminal” that can accommodate EMV and NFC transactions.

PayJunction uses interchange-plus pricing, which we here at Merchant Maverick believe will usually get you the best value overall. The cost of credit card transactions is interchange + 0.75%.

Given the breadth of PayJunction’s services, there’s a lot that you can do with its API. Setting up a development sandbox is pretty easy. The documentation is thorough, but it’s not laid out quite as intuitively as it is with some of the other services we’ve covered; expect to have to do a bit of scrolling to find the exact references you’re looking for.

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6. Braintree

Braintree Payment Solutions



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Pros

  • Predictable flat-rate pricing
  • Excellent developer resources
  • Integrates with PayPal

Cons

  • Overpriced gateway only option
  • Not suitable for high-risk industries

Braintree is part of the PayPal payment services family, along with sister services PayPal and Venmo. It does, however, function semi-autonomously from the other companies and has a slightly different focus.

At first glance, Braintree’s profile is very similar to Stripe’s — they both combine payment services and gateway functionality, with an eye toward international eCommerce. There are two important differences at this level, however. The first is that Braintree provides a merchant account rather than third-party processing, so you’re getting better account stability, but you should expect to have to jump through some additional hoops and wait times to set it up. And unlike Stripe, it is possible just to use Braintree as a payment gateway if you already have a merchant account. I wouldn’t recommend this, though, as using Braintree’s gateway à la carte is more expensive than most other independent gateways.

For developers, Braintree provides sandbox accounts to explore the service’s functionality. The online documentation is extensive if not quite as slickly presented as Stripe’s — you have to toggle between programming languages at the top of each page rather than each code snippet, for example. The payment API reference section for developers is well laid out, however, making it easy to look up the methods you’ll need when you need them.

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7. Adyen

Adyen



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Pros

  • Ideal for international merchants
  • No monthly fee
  • Good developer resources

Cons

  • Monthly minimums
  • Not suitable for high-risk industries

Adyen is a merchant account provider popular with some big-name companies, such as eBay, Spotify, and Microsoft. If you’re wondering why a Dutch payment services company is so popular with American corporations, it’s because this company excels at international transactions.

Adyen uses an unusual hybrid pricing system. Visa and Mastercard payments are processed using interchange-plus pricing: interchange rate + $0.12. Discover and American Express, on the other hand, are processed using a flat rate of 3.95% + $0.12. If you’re using a digital wallet, the pricing is connected to the attached card.

Adyen’s API allows you to build integrations that work with its infrastructure. There’s a lot here to work with, so Adyen breaks its documentation up into a number of topics — online payments, point of sale, plugins, etc. — that you can expand to find tutorials and references for the type of project you’re approaching. There’s also a convenient API Explorer you can use to find methods instead of having to scrub through the references.

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8. Authorize.Net

Authorize.Net



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Pros

  • Versatile payment gateway
  • Excellent customer support
  • Live console available in the documentation
  • Excellent developer resources

Cons

  • It can be expensive if not bundled
  • It is not a standalone solution

Most of the other services on this list have been payment processors. Authorize.Net, however, is a standalone payment gateway offered by Visa. You’ll often see it bundled with other services (which is how we’d recommend you use it).

As a payment gateway, Authorize.Net can connect your online store to your payment processor, provide support for multiple currencies, add security features, provide recurring billing services, and enable echeck processing.

In terms of developer resources, Authorize.Net may be one of Stripe’s closest rivals. There’s a ton of documentation, including API references, developer guides, and a collection of PCI-compliant tools called the Accept Suite. Most of it is publicly viewable, so you can check it out before you commit to anything. Much of the documentation contains an API live console, so you can test out snippets of code without leaving the resources.

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9. Helcim

Helcim



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Pros

  • Transparent interchange-plus pricing
  • No long-term contracts
  • Good developer resources
  • Accepts international payments

Cons

  • Not suitable for high-risk industries

Helcim is one of our favorite payment processors, and it’s not too hard to see why. Helcim offers transparent interchange-plus processing, no long-term contracts, and extensive fee disclosures. Not only that, but it also scales well with business growth and can handle international payments.

Compared to some of the other services on this list, Helcim’s developer tools fall somewhere in the middle of the pack. They’re more than serviceable, however, with a folder-like layout and ample screenshots. The Helcim API is a RESTful API and can be used with any language that can make an API call. In an interesting desktop layout choice, code samples live just offscreen and can be slid on or off the center of your screen with a click.

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Looking For One Of These Payment Processing APIs?

As you may have guessed, payment processing APIs are fairly common these days. In selecting our “best of” list, we tried to weigh the strengths of the base service and how well its developer tools stack up to the competition. That said, there are some great services with limited APIs as well as mediocre services with above-average developer tools. In other cases, the service might be extremely niche.

Here are a few services worth mentioning that didn’t quite make our list.

Google Pay

Google Pay allows customers to use payment methods saved to the Google account at checkout. This can be a nice convenience for your customers, particularly Android users. And, of course, you’ll get the developer experience you’d expect from the search engine giant, with a massive API library and exhaustive array of tools.

So what’s the issue? Well, your payment services provider needs to support Google Pay, which limits your options. It is still possible to add Google Play as a direct integration even if your provider doesn’t, but that means taking on PCI compliance yourself (and will require certification).

Amazon Pay

Similar reservations apply to Amazon Pay. It can be a great convenience to your customers, allowing them to use credit cards saved to their Amazon account in your store as well. This comes with some drawbacks, however, as Amazon releases payments, not after sales but after the customer receives the purchased items.

Amazon Pay’s developer tools are solid, if slightly underwhelming considering that it’s Amazon.

WePay

WePay is a popular white-label payments provider with good developer tools and an opaque and complex pricing system. WePay integrates with many established commerce platforms, such as Zoho and Classy, typically without the need for any developer intervention.

There’s nothing really wrong with WePay; it’s just up against some savage competition in the form of Stripe, Square, and PayPal, three of which have top-tier developer resources.

GoCardless

GoCardless is a global network designed for recurring payments. Within the US, GoCardless uses the ACH system to directly debit bank accounts (other methods are used in other markets). GoCardless provides both a simple payment integration tool and a developer API to add functionality to your website or app.

The developer tools look good, if not spectacular, but the service still seems fairly niche. We’ll keep an eye on it for future updates, however.

What To Look For In A Payment Processor API

Payment gateway API

What makes a good payment processor API? There are a few factors I’d keep in mind when you’re looking for a developer-friendly payment processor.

  • Does it offer support for multiple payment methods? While this may not be the case for every business, one of the most common reasons to use an online payment API is to expand and customize the payment methods you can offer your customers.
  • Is it customizable? All payment APIs offer some customization options, but does it just allow you to tinker around the edges, or does it offer enough depth to enable you to build what you want to build?
  • How is the pricing? Pricing is still the name of the game, no matter how much hacking you plan on doing. Make sure the provider’s pricing scheme works with your transaction volume and, preferably, allows for month-to-month contracts.
  • Is it secure? Most of the services above use some form of tokenization, so credit card information never ends up residing on your machine. Depending on the company, your PCI responsibilities may vary, so make sure you read through their documentation to find out what they take care of and what they don’t.
  • Does it have good and visible documentation? Many payment service providers offer payment APIs, but many of them hide them from the public. As a rule, I think it’s a good idea to be able to skim their documentation and get a sense of whether it’s a tool you want to work with.
  • Does the service provide SDKs and useful tools? Your mileage may vary here depending on your preferences, but some developers may appreciate having custom libraries and other labor-saving perks available to them.
  • Does it have an active community? Poke around the forums and see how active a developer community the product has. The more active it is, the more likely you’ll be able to have questions answered quickly and be able to make use of existing integrations and code.

Payment Processing Costs & Payment APIs

While some APIs are free to use, that’s not the case when it comes to payment processors. If you’re using a payment API, that usually means you’re going to have to be a customer of that payment processor.

That said, costs will vary greatly depending on the payment processor. Some processors, such as Stripe, will give you access to their API as part of the basic service. Since it’s a month-to-month service with no monthly fee, you’ll only pay the transaction costs, plus any premium features you sign up for. With other payment processors, the API may only be available if you are buying a premium plan.

Costs for payment API usage may include:

  • Transaction Fees: This is the amount of money that will be deducted from each of your sales. This amount will vary by payment method. While it’s usually the same regardless of whether you’re using an API or not, some APIs may allow you to use surcharging to pass on some costs to your customers.
  • Monthly Fees: These are membership fees you pay to keep your account going. Not all processors charge monthly fees. Some will only charge monthly fees for premium plans.
  • Gateway Fees: APIs are frequent functions of payment gateways. Some payment processors have integrated payment gateway APIs, while others use third-party gateways. Be aware of any additional monthly or transaction fees you have to pay to use a payment gateway.

How To Choose The Best Payment Gateway API For Your Needs

Now that we’ve covered some of the heavier hitters in the payment processing API department, you should be able to dig in a little further and match their capabilities to your needs. Remember that a service that is the best for one company may be an awkward fit for another. Take stock of your developers’ strengths and encourage them to poke around publically available documentation; they can give you a good idea of whether the platform can be hammered into the shape you want.

If you’re going to be tinkering with a payment API, it might be a good time to brush up on PCI compliance and security features, such as tokenization and fraud detection. If you’re looking to customize your payment workflow, you may also want to read up on alternative payment methods.

In Summary: 9 Best Credit Card & Payment APIs For Developers

  1. Stax by Fattmerchant:
    • Subscription-based pricing
    • Quick access to API sandbox
  2. Square:
    • Versatile toolset
    • Good documentation
  3. Stripe Payments:
    • Top-tier developer support
    • Strong developer community
  4. Dwolla:
    • Strong developer support
    • Unique payments platform
  5. PayJunction:
    • Excellent merchant services
    • Test server available
  6. Braintree Payment Solutions:
    • Exhaustive developer resources
    • Can access PayPal's ecosystem
  7. Adyen:
    • Strong international support
    • Easy-to-parse documentation
  8. Authorize.Net:
    • Versatile payment gateway
    • Excellent dev tools with live console
  9. Helcim:
    • International payments with interchange-plus pricing
    • Good developer tools
Chris Motola

Chris Motola

Expert Analyst & Reviewer at Merchant Maverick
An expert in personal and business loans and financial health, Chris Motola has been writing about small business finance and payments for over 5 years. He has been cited in various industry publications, including Forbes Advisor, GoBankingRates, and Medium. Chris is a graduate of the University of Central Florida.
Chris Motola
View Chris Motola's professional experience on LinkedIn.
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