What Are Payment APIs & How Do They Work?

Payment APIs give businesses more options for accepting online payments.This is especially important if you’re considering setting up a new business or moving your in-store business online.

A payments API provides the crucial link between a business’s e-commerce store and its payment gateway. Because payment APIs contribute to the security and smooth functioning of the payment process, it’s essential to choose the right payment API for your business.

What Does “API” Stand For?

The acronym “API” stands for “application programming interface.”

What Are APIs?

APIs are modules from third-party service providers that function as a go-between for two different pieces of software. They allow developers and site builders to use applications without the need to build the code themselves.

Developers must understand which features are available as an API and how to implement that API into a preexisting site. They can then upgrade or improve the site’s functionalities quickly and effectively.

APIs Often Need to Be Customised

Developers will still often have to make small adjustments or customisations to make the API work for each specific project. This could be something as simple as adding branding to the application or adjustments that are necessary to make it work on an alternative platform.

API creators often provide support to developers. This ensures that their API technology is used consistently and competently across all platforms.

What Are Payment APIs?

Payment APIs are APIs that help online businesses facilitate payments. They offer security, consistency, and seamless integration with a wide range of e-commerce platforms. They’re also beneficial from a business’s perspective as they take away the burden of meeting constantly evolving compliance regulations in-house.

A payment API can be offered by a payment processor or a payment gateway provider. In both cases, the goal is the same: to allow businesses to collect payments and customers to complete purchases without having to leave the business’s e-commerce website.

Payment APIs offer security measures for the business and the customer. Added security features make customers feel safe when making a purchase online and protect companies against potentially costly errors that may occur when in-house developers create their own checkout solutions.

According to a recent Allied Market Research report, the online payment API market was valued at $200.0 million in 2023 and is projected to reach $306.5 million by 2032, reflecting the growing reliance on secure, API-driven payment infrastructure.

A Payment API Is One Type of Payment Gateway

There are three types of payment gateways: hosted, self-hosted, and API-hosted payment gateways. The third option offers a solution that takes some of the best features from the other two, making it an appealing solution for many businesses.

Why Choose an API-Hosted Payment Gateway?

Businesses should choose an API-hosted payment gateway because it allows them to enjoy all the customisable features of a self-hosted gateway and the technical support provided by the company that produced the API. This is often a merchant account provider.

Payment processing through an API-hosted payment gateway involves integrating the payment gateway into the merchant’s website. However, the payment process will still be in line with your branding and any customisations you want to make.

API-hosted payment gateways are typically integrated into the checkout via a plugin or software module. This code will be pasted into your existing site to be branded and customised as you see fit. At Unicorn Group, for instance, we offer API modules for all the primary shopping carts. New software modules can also be created on request.

API-hosted payment gateways offer advanced payment options that allow merchants to accept payments from other countries using different payment methods. This is especially important for businesses in Europe that sell products across borders.

How Do Payment APIs Work?

A payment API works by connecting an online store with the merchant’s chosen payment processor during checkout. The API connects directly to the payment network.

There are three steps in the payment process:

• Authorisation: The customer’s card-issuing bank authorises the payment.
• Capture: The funds pass from the issuing bank to the merchant’s acquiring bank.
• Settlement: The funds are transferred to the merchant’s business bank account.

The API allows you to see the payment status for all of your transactions using webhooks. Please note that there may be a delay for payment methods like bank transfers (via SEPA or ACH) and intentionally delayed-capture transactions, such as those involving a pre-authorisation charge.

A pre-authorisation charge is a hold that’s placed on a certain amount of funds on the customer’s credit card, but capture is delayed. This is useful for businesses like hotels and rental companies that need the customer’s card details to provide the service, but the total amount to be billed is not yet finalised.

Benefits of Payment APIs

Payment APIs offer several benefits in addition to those mentioned above:

Faster Time-to-Market

Payment APIs allow you to start accepting payments in as little as 12 hours, as opposed to months spent building your own payment gateway from scratch. Some payment gateway providers even offer free integration support to businesses that don’t have a web development team to input the necessary coding for integration.

Lower Regulatory Burden

Tokenised payment APIs store data and process payments entirely off your website, so you don’t need to worry about PCI compliance on your end. This reduces risk and liability significantly, and provides peace of mind to small businesses that would struggle to cover the cost of a data breach (which averaged $4.4 million USD globally in 2025).

Adaptable to Your Business Model

Payment APIs are very flexible and enable many different payment types. For example, they handle both one-off and recurring payments. This is beneficial for businesses that want to adapt the payment process to their business model. It also makes the payment process easier for the customer.

Customisable Features

Being able to customise payment APIs means you can tailor them to your business’s specific needs. This could include adding features that enable recurring payments. Real-time reporting features are also useful for businesses that manage a large inventory or receive a large amount of suspicious transaction requests.

Offer Various Payment Methods

Payment APIs can also be used in tandem with other payment APIs from different payment solutions and gateways, thanks to their ability to be customised. This is beneficial because it allows developers to combine the best features of several payment APIs or add a payment method when requested by the merchant.

Why Is It Important to Process Different Payment Methods?

It is important to be able to process different payment methods because this allows you to capture the maximum number of sales. Payment solutions are constantly evolving. 72% of European consumers use mobile payments like Google Pay and Apple Pay. This is in addition to more traditional payment methods like credit card, debit card, bank transfers, and cheque.

Automated Support

APIs typically offer retailers several automated support services. This includes verification of the customer’s payment information and fraud detection. Payment APIs also provide data in real-time on a transaction’s status and any relevant payment history. All of these features help merchants streamline their payment processes, reduce costly errors and fraud, and increase customer trust.

Payment API Security & Compliance

Every website that stores customer payment data must comply with Payment Card Industry Data Security Standards (PCI DSS). This responsibility is shared between the host website and the payment processor when a payment API is used.

Tokenisation and encryption are two common ways customer payment information is kept secure online. Whereas tokenisation replaces the card details with a token, encryption scrambles the card details and is unscrambled at the receiving end with a key.

Businesses in Europe must additionally comply with the Payment Services Directive 2 (PSD2) and Strong Customer Authentication (SCA). For e-commerce businesses, this typically means that customers need to complete two-factor or multi-factor authentication checks, using biometric authentication or a code sent to their e-mail address or mobile phone.

Business Types That Use Payment APIs

Many types of businesses benefit from using payment APIs:

Online Retailers

APIs are primarily associated with online retailers that sell goods or services via e-commerce websites.

Online Marketplaces

Payment APIs are used by online marketplaces to take payments from customers, split the revenue between the sellers and the marketplace, and settle the funds to the sellers’ bank accounts.

SaaS and Subscription Businesses

SaaS and subscription companies benefit from payment APIs to handle recurring payments from customers online.

Mobile App Businesses

APIs provide a convenient and accessible way for creators of mobile apps to process app sales and in-app purchases.

Brick-and-Mortar Businesses

Some brick-and-mortar businesses that take payments online might also use payment APIs.

Individual Business Owners

Freelancers and consultants are increasingly using payment APIs to facilitate payments from their customers.

Other businesses may use a payment API without even realising it. Anyone who accepts online payments is generally using a payment API.

How Much Do Payment APIs Cost?

The cost of a payment API will depend on which one you choose and the services offered. Some payment APIs are free of charge, while others come with subscription fees and/or per-transaction fees.

How to Set Up a Payment API

Complete the following steps to set up a payment API on your e-commerce website:

• Account approval (1-2 days): Apply to a payment provider and provide the required documentation for the underwriting process. The provider will review your application and notify you of approval.
• Sandbox testing: (1-3 days): Your team will work in a sandbox environment to simulate transactions and make sure everything works correctly.
• Integration and Quality Assurance (1-3 days): Your web developer (or your provider’s web development team) will write the necessary code to integrate the payment API into your website. Ready-to-go API modules will be significantly faster to integrate, sometimes taking one day or less.
• Go Live (1-3 days): Production credentials are issued, and you start processing real transactions with live API keys instead of sandbox keys.
• Post-Launch Monitoring (ongoing): From here, monitor live transactions to check for errors or system downtime, check for API version updates, and reconcile transactions with the payouts shown on your bank statements.

Tip: Want to start selling faster? Go for a hosted payment page that doesn’t require much coding for integration.

Payment API Setup Checklist

Use this checklist to ensure a successful payment API setup process.

How to Choose a Payment API

It’s important to do your research when choosing from among several payment API options. Take the time to find one that’s compatible with the technology you currently use and offers the services your business needs.

Basic features to look for in a good payment API include:

• International payment support: A payment gateway that supports multiple currencies and payment methods for international customers
• Maximum uptime: Ask about uptime averages and guarantees. 99.99% uptime is preferable, as any downtime will affect sales, revenue, and customer satisfaction
• Ongoing technical support: Access to support staff and frequently updated manuals or resource guides
• API client libraries: Cut-and-paste code in a common programming language to help businesses get going without spending a long time learning how coding works
• Reliable, useful, and relevant updates: Automatic and when needed
• Secure credentials: API keys or other robust security measures to protect access
• Testing opportunities: An opportunity to try out an API before you take the plunge and take it live on your site

Customised Payment Processing Is Easy With APIs

Payment APIs can be moulded to your business’s payment processing needs, whether you’re running a very small local business or a multinational enterprise. The right payment API provider will understand your business and have the ability to scale with you as you grow.

An API-hosted payment gateway with a connected merchant services account is the perfect solution for online stores that require effortless payment processing and a wide variety of payment options. The right payment API will also offer security features to keep your business and customers safe.

Published: March 25, 2024
Last updated: February 23, 2026