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6 Best Credit Card Processing APIs for Your Business in 2023

Emma Ayres Emma AyresFinance Specialist November 29, 2022
November 29, 2022
The great thing about e-commerce payment technology is that it’s relatively easy to customize. All you need is some experience using Application Programming Interfaces (APIs) – or a willingness to learn – and a credit card processor that offers this helpful development toolkit.

With that being said, not every payment processor offers an API. Those that do rarely provide adequate documentation to properly implement their API, or their API only support a few coding languages. Even if a merchant services provider offers great value in other areas, not having the tools you need to build custom e-commerce integrations and applications can be hugely limiting.

After researching dozens of credit card processing services, I’ve put together a list of those that offer a great range of APIs to help you get the most out of their respective software suites.

Whether you want to build custom integrations or need a developer kit that has API templates for shopping carts and checkout pages, my list will have a payment processor that has what you’re looking for.

Short on Time? These Are the Best Credit Card Processing APIs in 2023

  1. Stax – A Level 1 PCI-compliant payment processor with a well-documented and secure API.
  2. Payment Depot – A budget-friendly payment processor that provides Authorize.net’s award-winning API.
  3. Leaders Merchant Services – Offers a range of APIs, including Authoize.net and the free Google Pay API.

See 3 More Great Options | Comparison Table | FAQ

What We Look For in the Best Credit Card Processing APIs

Not every developer kit and API library is built equal. That’s why I made sure every payment API on my list offers these features.

  • Comprehensive documentation. Having well-written and detailed documentation means you don’t have to spend hours trying to decipher API code, error responses, and access tokens.
  • Wide range of supported languages. A well-built API should support multiple programming languages, regardless of the software that will connect to the API. The more languages that a payment processor’s developer kit supports, the better.
  • Sandbox. A sandbox lets you test your API in a sandbox environment so you can make sure it works before you deploy it to your working environment. This means you’re not risking harming your customers’ e-commerce experience by testing your API on your live website.
  • Security. Because the API will be handling sensitive financial data, the payment processor needs to ensure it is built with a security-first approach. This includes enforcing the use of hashing, SSL certificates, and developer authentication via API access tokens.
  • PCI compliance support. Every API offered by a payment processor needs to be PCI-compliant. However, if you’re using the API to build checkouts that are hosted on your website, you’ll have to fill out a different questionnaire to ensure that you’ve met testing and security requirements. Your payment processor should offer support with this.

Stax summary
You can use Stax’s API to build custom checkouts and integrations
When it comes to credit card processing APIs, Stax is one of the best on today’s market. Its documentation library is among the most comprehensive I’ve seen from a payment processor, covering everything from setting up a sandbox environment to using Stax’s JavaScript library (Stax.js). On top of that, you don’t need to pay any extra fees to use Stax’s modern software or developer kit thanks to its simple subscription-style pricing. It’s easy to see how most businesses can save up to 40% with Stax.

This API is also Level 1 PCI-compliant and has a variety of built-in security features like rate limiting, tokenization, and address verification (AVS). The Stax.js library also contains multiple validation events that can protect your databases from injection attacks by ensuring that only data that meets the expected input is pushed to your database.

Because it comes with an SDK library for iOS and Android, you’ll also be able to use Stax’s API to set up custom mobile payments. This allows you to set up custom mobile payment apps using Stax’s PCI-compliant framework. You can use this as a base to add custom-built features like multi-currency transactions – something that Stax doesn’t normally offer.

Features and Benefits

  • Embeddable payment forms. Some customers will abandon their cart if they’re redirected to the webpage of a third-party gateway when it’s time to pay. Stax.js allows you to embed a payment form into your website to reduce cart abandonment and improve trust with your customers.
  • Language agnostic. Stax’s API is designed to work with any language that can interact with REST API, enabling you to use this API with a wide variety of software suites.
  • Quick-start guide. Stax has a quick-start API guide that shows you how to set up sandbox and production accounts, how to use Stax.js, and how to generate API keys. While this document is relatively short, it has quick links to other documentation pages so you can quickly find what you need.
  • PCI compliance support. Merchants using self-hosted payment APIs usually have to undergo a lengthy assessment. With Stax, you’ll get access to a third-party PCI compliance dashboard that will alert you when your security assessment is due and guide you through the questionnaire.
Read our expert Stax review to discover more great payment features.

API availability Pro and Ultimate plans
Developer support
  • Full documentation
  • Quick-start guide
  • Sandbox
  • SDKs
  • JavaScript library
API security features
  • AVS
  • CVV
  • Rate limiting
  • Tokenization
  • Testing parameters
Transaction fees on cheapest plan with API 0% + 8¢ (in-person)
Monthly subscription on cheapest plan with API $99.00

Payment Depot summary
Payment Depot’s pre-built integrations and shopping carts are really helpful
Stax isn’t always a wallet-friendly solution for smaller businesses. Payment Depot offers an affordable alternative. With a similar suite of integrations and pre-built shopping carts, and monthly plans starting at only$59.00, Payment Depot offers significant savings for small high-volume businesses. While it doesn’t offer an API itself, it integrates with Authorize.net.

Authorize.net offers an award-winning API with plenty of helpful developer tools, so it’s not surprising it’s one of the most popular payment gateways on the market. You’ll get pre-built, mobile-friendly payment forms, the ability to build digital wallets, and SDKs so you can integrate payment forms into your own mobile applications.

Not only that, but there are no additional fees to use Authorize.net with Payment Depot. Many payment processors charge a few extra dollars each month for you to use this payment gateway, so having it included in your monthly fee can save you a significant amount in the long run.

Features and Benefits

  • Accept additional payment types. Payment Depot doesn’t accept PayPal. However, Authorize.net has a pre-built PayPal integration that will allow you to accept this payment method.
  • Comprehensive documentation. Authorize.net has plenty of API reference documents, developer guides, testing guides, FAQ pages, and more. There’s even a public GitHub page and Stack Overflow forum.
  • Pre-built integrations. Payment Depot has multiple pre-built integrations for QuickBooks and Revel, as well as other popular business software. You’ll also get one-click shopping carts for some of the most popular e-commerce platforms – carts you’d otherwise have to build from scratch with Authorize.net.
  • Fraud protection. Authorize.net’s API has built-in fraud management features like AVS, velocity filters, transaction holds, and more. In combination with Payment Depot’s 24/7 risk monitoring, this can greatly reduce your business’s losses from fraud.
Read our Payment Depot review for more details on its included integrations.

API availability On all plans
Developer support
  • Developer forums
  • Comprehensive documentation
  • GitHub repositories
  • Sandbox
  • And more
API security features
  • AVS
  • CVV
  • Velocity filters
  • Transaction holds
  • Customer transaction profiles
  • And more
Transaction fees on cheapest plan with API 0% + 8¢ (in-person)
Monthly subscription on cheapest plan with API $59.00

3. Leaders Merchant Services: Multiple Payment API Options

Leaders Merchant Services summary
Leaders Merchant Services offers multiple payment solutions
While many payment processors choose to utilize just one API solution, Leaders Merchant Services (LMS) offers multiple developer toolkits. You can pay for the popular Authorize.net payment gateway’s developer kit or get Google Pay’s API for free. With Google Pay being one of the most trusted names in modern payment technology, this can help you to reassure those customers who don’t always trust third-party payment getaways.

LMS’s rates are some of the lowest in the industry, so being able to use the Google Pay API for free makes this payment processor a great budget-friendly solution. It’s not as comprehensive or detailed as Authorize.net’s API, but it still has all the features you’ll need to build custom payment solutions.

Google Pay’s API has a decent amount of documentation for web or Android applications. There’s a tutorial to show you how to download and deploy the Google Pay API, and a checklist to help you test an application before deployment. However, Google Pay’s API doesn’t support development on iOS.

Features and Benefits

  • Pre-built Google Pay buttons. Though you’ll have to adhere to Google Pay’s branding standards to use its API, you can customize the Google Pay button that appears on your site. You can change text, language, color, and sizing before copying and pasting the code directly into your website.
  • Only pay for what you need. Because Authorize.net is available at an additional cost, you don’t have to pay for it if it doesn’t suit your business.
  • Built-in QuickBooks integration. While you won’t be able to build custom integrations with LMS directly, it does offer a QuickBooks integration that allows you to sync your accounting data.
  • Payment card recognition. Google Pay’s API allows customers to use their device’s camera to capture their card details. This makes paying for your products or services quick and convenient and can lead to fewer abandoned carts, particularly because customers don’t need to have the Google Pay digital wallet for this to work.
Read our in-depth Leaders Merchant Services review for more details.

API availability On request
Developer support
  • Documentation and testing parameters
  • GitHub repositories, developer forum, and more (Authorize.net only)
API security features
  • AVS
  • CVV
  • Tokenization
  • Google account verification (Google Pay API only)
  • Velocity filters and transaction holds (Authorize.net only)
Transaction fees on cheapest plan with API Around 2% + 0¢
Monthly subscription on cheapest plan with API $10

Flagship Merchant Services summary
Flagship Merchant Services has a variety of virtual processing solutions
Flagship Merchant Services stands out because it offers the popular Authorize.net payment gateway and API for significantly less than some competitors. It only charges $7.95/month to use Authorize.net, which is almost 70% cheaper than the price charged by LMS.

It’s also one of the few processors that offer a same-day funding option. As with most Flagship features, this comes at an additional cost not advertised on the website. However, if you need a steady cash flow, it’s worth contacting Flagship for a quote.

Even though Flagship’s per-transaction rate is fairly high compared to other payment processors, you can – and should – negotiate your fees with Flagship to get a better rate. If it can’t at least match your current rate, you can get a $200 AMEX gift card under its Meet-or-Beat guarantee.

Features and Benefits

  • Great security features. In addition to Authorize.net’s built-in security features, Flagship uses tokenization to secure all customer and payment data on its servers. It’s also fully PCI, GDPR, and CCPA compliant.
  • 24/7 support. Both Authorize.net and Flagship offer 24/7 phone support, so you’ll always have someone to call if you need help with configuring your API or accessing any other features.
  • Quick setup. It only takes a few minutes to apply for a Flagship merchant account, and you can be approved in as little as a few hours. Once you’ve been accepted, you can start processing payments with Authorize.net on the next business day.
  • PCI compliance support. Flagship will regularly scan your merchant account to make sure that you’re fully PCI compliant.
See our comprehensive Flagship Merchant Services review for a full fee breakdown.

API availability On request
Developer support
  • Developer forums
  • Comprehensive documentation
  • GitHub repositories
  • Sandbox
  • And more
API security features
  • AVS
  • CVV
  • Velocity filters
  • Transaction holds
  • Customer transaction profiles
  • And more
Transaction fees on cheapest plan with API 1.58% + 19¢ (in person)
Monthly subscription on cheapest plan with API $7.95

5. Helcim: A Powerful API With Limited Support

Helcim summary
Helcim is one of the few payment processors that has its own custom API
With so many payment processors opting to integrate with third-party payment APIs, Helcim is one of the few that invests in its own developer toolkit. Helcim boasts over 80 different API actions, a JavaScript library, full documentation, and quick-start guides to help you configure the Helcim API to work with your own custom applications. What’s better is you won’t have to pay anything extra to use this, either – Helcim’s simple and transparent pricing model includes no monthly fees to use its software.

You also have two options for testing – you can either set up a sandbox, or you can use the in-browser code builder to test your pre-built API code to ensure it’s working correctly. You can also see how Helcim’s pre-built API templates work in the browser before you test them in the sandbox.

While Helcim offers a good level of support, the lack of a 24/7 support channel for developers is disappointing. All you’ll have are the provided guides and documentation. If you’ve got a lot of experience with APIs, then this lack of around-the-clock support isn’t necessarily a deal-breaker. However, it’s not ideal if you need more direction and support with Helcim’s API.

Features and Benefits

  • Built-in security. Helcim’s API uses secure ports, SSL certificates, and encryption keys, and the handful of ciphers it allows all provide a high level of data security. If the API can’t connect to Helcim’s server using a secure pathway, the server will refuse the request.
  • Helcim Card Vault. Customers can opt to store cards in their profile, which are tokenized and saved on Helcim’s servers. Helcim’s API can access this data, allowing you to build custom applications that make it as convenient as possible for customers to pay you.
  • Helcim Fraud Defender. You can use Helcim’s API to connect to Fraud Defender, which checks specific card transactions for fraudulent activity. Fraud Defender will then give you an analysis of that customer’s history, AVS, and more.
  • Hosted payment pages. Helcim’s API allows you to build checkout pages where captured payment data is sent through Helcim’s servers rather than yours. This reduces the risk of a data breach and means you don’t have to worry about making your own server PCI-compliant.
Read about our experience with customer support in our in-depth Helcim review.

API Availability On all plans
Developer support
  • Full documentation
  • Sandbox
  • Limited in-browser testing
  • JavaScript library
  • Quick-start guide
API security features
  • CVV
  • Tokenization
  • SSL
  • Encryption
  • Hashing
  • Helcim Fraud Defender
Transaction fees on cheapest plan with API 0.30% + 8¢ (in-person)
Monthly subscription on cheapest plan with API

6. Luminous Payments: Pay Less for a Good API

Luminous Payments summary
Luminous Payments focuses primarily on in-person sales but offers NMI for e-commerce
If you like the look of Authorize.net but you don’t have the budget for its (usually) high monthly cost, take a look at Luminous Payments. Luminous Payments offers five different pricing models, so it’s easy to negotiate the best deal for your business.  On top of this processor’s flat monthly fee, you can get the NMI gateway and API for only $6/month.

While NMI’s API is relatively basic, it’s by no means bad. It has everything you need to set up payment forms, custom integrations, and even cloud-based terminals. Each API action is fully documented with a quick setup guide, testing parameters, and troubleshooting documentation.

Even though it offers NMI for a low price, Luminous Payments isn’t for everyone. It focuses on local, in-person businesses, and its e-commerce functionality is limited to what’s offered by NMI. If you handle more than a moderate number of transactions online, Luminous Payments might be too limiting for you.

Features and Benefits

  • Quick-reference tables. You’ll find quick-reference tables covering error codes, recovery tips, event types, and more within NMI’s documentation. This can help you to cut down the time it takes to test your API as all the information you need is in one place.
  • SDK library. NMI’s SDK library works with iOS, Android, Windows, Linux, and popular POS terminals. There’s even a Windows SDK emulator that allows you to take in-person payments without needing POS hardware.
  • Third-party shopping carts. NMI has over 125+ pre-built shopping cart integrations for a wide variety of e-commerce platforms, website builders, content management systems, and more.
  • Same-day setup. Luminous Payments aims to get all merchants set up on the same day your application is accepted. While you’ll have to wait a few days to start taking payments, you’ll be able to set up the NMI gateway and use its developer kit straight away.
Read our expert Luminous Payments review to see how it can help your business.

API Availability On request
Developer support
  • Full documentation
  • Quick-start guide
  • JavaScript library
  • SDK library
API security features
  • CVV
  • End-to-end encryption
  • SSL
  • Tokenization
  • Testing parameters
Transaction fees on cheapest plan with API 1.59% + 5¢
Monthly subscription on cheapest plan API $10.00

Which is the Best Credit Card Processing API?

If you want to build custom e-commerce features, you’re going to need a well-documented and comprehensive credit card processing API that you can easily integrate with your current e-commerce solutions.

Overall, I recommend Stax API because it offers the best range of API actions and SDKs. The available documentation is comprehensive and clear, and it’s always easy to find what you’re looking for within its easy-to-use developer toolkits.

If you don’t have the budget for Stax, then Payment Depot is a great choice. While it’s a subsidiary of Stax, it helps you to save money by outsourcing its API functions to the popular third-party gateway Authorize.net. And unlike some other processors, it doesn’t charge any additional fees to use this gateway.

For an even more affordable option, I recommend Leaders Merchant Services. Because it uses interchange-plus pricing, it’s the best choice for lower-volume businesses. And though it charges extra for use of Authorize.net, you can opt to use Google Pay’s API for free, helping you to keep your costs low.

Keep scrolling for a quick comparison of the best payment APIs.
Best Feature Best For Monthly fee on cheapest plan with API Transaction fees on cheapest plan with API
Stax Fully-documented API with built-in security features Businesses that need secure custom payment solutions for websites and mobile apps $99.00 0% + 8¢ (in-person)
Payment Depot Authorize.net included in your Payment Depot plan Businesses that need an industry-leading payments API without the high cost $59.00 0% + 8¢ (in-person)
Leaders Merchant Services The choice between Google Pay’s API or Authorize.net Budget-conscious businesses that only want to pay for the software they need $9.00 Around 2% + 0¢
Flagship Merchant Services Negotiable rates with affordable access to Authorize.net Businesses that are happy to negotiate for a custom payment solution $7.95 1.58% + 19¢ (in person)
Helcim A unique API with over 80 available API actions Businesses that don’t want to pay extra each month for a third-party gateway 0.30% + 8¢ (in-person)
Luminous Payments Access to an industry-leading payment API for a few dollars a month Businesses that need a basic payment gateway API $10.00 1.59% + 5¢

FAQ

What is a payment gateway API?

A payment gateway API is a relatively short section of code that allows your payment gateway or payment processor to integrate with another software. These APIs allow merchants to build custom payment forms and shopping carts. Some processors like Stax develop their own APIs and include them for free – this ensures that the API works seamlessly with their software while also saving you money.

Which credit card processing API is best?

All things considered, Stax’s API is probably the best. Not only is it fully documented, it also has some great security features built into it. It automatically uses tokenization to keep sensitive data secure and rate limiting to prevent potential denial-of-service attacks. It’s also designed to work with most developer languages.

What’s the difference between a payment gateway and a payment processor?

A payment gateway captures and transmits payment information between your point of sale (whether that’s in-person or online) and the payment processor. The processor then relays this information from the customer’s bank to the merchant’s bank. Some payment processors – like Stax – develop their own payment gateways, while others – like Payment Depot – offer merchants a third-party payment gateway that connects to their processing service.

Which payment gateway is most popular?

PayPal and Stripe are two of the best-known payment gateways, but they’re not always the best choice for your business. They typically charge higher-than-average fees and they don’t come with additional processing features you might need, like card terminals and third-party POS integrations. Many of our top 10 credit card processors in 2023 have their own payment gateways or use industry-leading third-party solutions, despite being considerably cheaper.

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