8 Best Credit Card Processing APIs for Your Business in 2023

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.

Overall, I found that Leaders Merchant Services (LMS) offers the best APIs of all the payment processors on this list. In addition to offering multiple developer toolkits, including a free one, it provides all the necessary documentation and a sandbox testing environment. LMS’s API library also contains plenty of built-in security features.

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.

1. Leaders Merchant Services: Low Rates With Multiple API Options

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 gateways.

LMS’s rates are some of the lowest in the industry, starting at only $9.00/month. 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.

2. PAYARC: Robust Free API and International Support

PAYARC offers a robust free API and Software Development Kit (SDK), allowing you to personalize its payment systems to your specific needs. It also provides free API guidance to get the most out of its platform. Once you log into your dashboard, you can obtain your API token to incorporate functionalities like recurring, usage-based, and one-time billing, tiered pricing, and custom invoices. PAYARC doesn’t charge a fee for using its invoicing tools.

You can also use PAYARC’s API to integrate its proprietary payment gateway. At only $5/month, it’s one-fifth of what most processors charge for popular gateways like Authorize.net. As a PAYARC customer, you’ll also get access to the comprehensive Authorize.net API for a discounted monthly fee of $12.

Furthermore, PAYARC gives you access to a few international gateway APIs, enabling you to accept payments in 150+ currencies. The Planet Payment gateway, for example, is ideal if you need to collect payments from various channels like your website, social media accounts, email, and digital ads. It provides tools like secure credit card data storing and one-click payments for a seamless omnichannel payment experience.

Features and Benefits

• Diverse pricing structure. PAYARC’s flat rate pricing is a great fit for smaller businesses that process a lower volume of card payments. You’ll only have to pay a per-transaction rate of 2.49% + 30¢ (in-person) and 2.9% + 30¢ (online). If you process more, you can save with PAYARC’s membership-based plans starting at $69.00/month with fees as low as 0% + 15¢ (in-person & online).
• Well-written documentation. PAYARC provides thorough documentation for its API, and includes detailed implementation for a variety of uses, including subscriptions, disputes, webhook triggers, and payment pages.
• Coupons. PAYARC’s API lets you create custom coupons to offer special sales, run promotions, and attract new customers with first-order discounts.
• 24/7 support. PAYARC has a team of professionals available 24/7 on the phone to answer your questions and solve your issues. Alternatively, you can reach its support via email.

Our expert PAYARC review has more features to explore.

3. ProMerchant: Integration With Trusted API for All Kinds of Transactions

ProMerchant integrates with Authorize.net, which offers a comprehensive API full of helpful developer tools. You can build digital wallets and use SDKs to integrate payment forms into your sales channels, or use its pre-built, mobile-friendly payment forms.

Authorize.net also offers a virtual terminal that enables you to key in payments taken over the phone, email, mail, or text. Alternatively, you can process mail order/telephone order (MOTO) payments using the free Payments Hub virtual terminal. Payments Hub also offers its own comprehensive developer solutions for e-commerce and mobile apps.

ProMerchant provides free POS hardware, which, combined with its e-commerce features, is ideal for businesses that sell both in-person and online. Its interchange-plus plans start at $7.95 and are some of the industry’s lowest. However, its transaction fees of 3% + 10¢ (credit) are slightly higher than LMS’s fees. If you run a restaurant or retail business, you can opt for its zero-cost processing program.

Features and Benefits

• Customer profiles. With Authorize.net’s API, you can store customer billing, payment, and shipping details. For about 25¢ per update, you can refresh credit card data, reducing payment interruptions.
• Easy invoicing. Authorize.net allows you to send email invoices using a “click to pay” link, along with reminders for unpaid invoices.
• Automatic recurring billing. Using Authorize.net’s API, you can set up monthly or custom automatic billing monthly. This removes the need to re-enter customer information and ensures you always get paid on time, boosting your cash flow.
• Simple checkout. With Authorize.net’s API, you can add a “Buy Now” button to your website for a frictionless payment experience.

To see more benefits, take a look at our full ProMerchant review.

4. Flagship Merchant Services: Cheap API and High-Risk Merchant Accounts

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 most processors charge. But there’s a catch: You’d have to pay extra for full access to Authorize.net’s robust software and Flagship’s in-house support.

Starting at $7.95/month, Flagship’s plans include the essentials. This approach means you’ll never pay for features you don’t need. However, it can prove costly if you do need a range of features. Flagship’s per-transaction interchange rate of 3.58% + 0.19¢ (in-person) is fairly high compared to other processors, but you can negotiate your fees for a better rate. If it can’t at least match your current rate, you’ll receive a $200 AMEX gift card under its Meet-or-Beat guarantee.

Flagship boasts a 98% approval rate. This means it will likely accept your application even if you’re a new business with no credit history, have a low credit score, or operate in a high-risk sector like cannabis, multi-level marketing (MLM), and travel and hospitality.

Features and Benefits

• Quick setup. Applying for a Flagship merchant account only takes a few minutes, and you can begin processing in as little as a few hours. Once accepted, you can take your first payments with Authorize.net on the next business day.
• 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.
• Fast funding. Flagship offers same-day funding as an optional add-on, a handy feature for new businesses that need steady cash flow.
• PCI compliance support. Flagship will regularly scan your merchant account to ensure you’re fully PCI compliant.

See our comprehensive Flagship Merchant Services review for a full fee breakdown.

5. Stax: Secure, Well-Documented API for High-Volume Businesses

Stax’s documentation library is among the most comprehensive I’ve seen from a payment processor. It covers everything from setting up a sandbox environment to using its JavaScript library (Stax.js). You can also use Stax’s PCI-compliant framework as a base to add custom-built features like multi-currency transactions – something that Stax doesn’t normally offer.

Stax’s API is 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.

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 starting at $99.00/month. Compared to other payment processors, Stax’s low per-transaction fees of 0% + 10¢ (in-person) could result in savings of up to 40%. However, its pricing model works only for merchants processing at least $8,000 monthly transactions.

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.

6. Helcim: A Free API for Budget-Conscious Businesses

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.

Other Notable Credit Card Processing APIs

7. Chase Payment Solutions

Chase Payment Solutions provides a variety of proprietary and third-party APIs that cater to small and medium-sized businesses (SMBs) and Software as a Service (SaaS) companies. For SMBs, it provides APIs for the Orbital gateway and virtual terminal, digital wallets, e-commerce solutions, and more. It also has a few WePay developer kits for SaaS companies. With the WePay APIs, you can brand Chase’s payment solutions as your own.

While Chase has an extensive suite of APIs, it might not fit every business. It doesn’t cater to high-risk merchants. Some of its APIs also require developer support, which could be expensive for small and growing businesses. However, Chase might be a good choice if you have the necessary resources and deal with complex payment needs.

8. CreditCardProcessing.com

CreditCardProcessing.com doesn’t have its own API but offers limited access to the Authorize.net API at a quarter of its regular price. This could be a great option if you can handle everything on your own and have a fair knowledge of how to integrate APIs.

This processor offers affordable subscriptions with lower-than-usual transaction fees for high-volume businesses. It’s worth mentioning that CreditCardProcessing.com’s interchange-plus pricing isn’t the best, though. There are also additional fees to access customer service, which is typically free elsewhere. You can likely negotiate a better deal at LMS if you run a small business.

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.

Leaders Merchant Services (LMS) is the best choice for most small businesses, including those processing a lower volume of card sales. It offers some of the industry’s lowest interchange-plus pricing and you can negotiate your rates and tailor your plan. While LMS charges a fee for using Authorize.net’s API, you can use Google Pay’s API for free, which is a great way to keep your costs down.

If your business is growing and you’re expanding into international markets, I recommend PAYARC. You’ll get free access to PAYARC’s extensive APIs and SDKs, plus API onboarding. For a low fee of $5 per month, you can integrate PAYARC’s proprietary gateway. You can also integrate some of its third-party international gateways.

ProMerchant is another great option for businesses that operate both in-person and online. It offers integration with the trusted Authorize.net API, which provides access to additional security features. It also provides a virtual terminal through Authorize.net and Payments Hub at no extra cost. Additionally, you’ll receive free POS hardware to support your in-person operations.

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 and PAYARC 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?

It depends on your needs. Leaders Merchant Services (LMS) offers a few developer toolkits, such as the comprehensive Authorize.net API and the free Google Pay API. Authorize.net’s API is fully documented, includes some advanced security features, and allows you to build custom payment solutions. LMS’s custom pricing model means you only pay for Authorize.net when necessary, saving money if the free Google Pay API meets your requirements.

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 Helcim) develop their own payment gateways, while others (like ProMerchant) offer merchants a third-party 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.