REST API
A REST API (Representational State Transfer Application Programming Interface) is a web-based interface standard that uses HTTP protocols such as GET, POST, PUT, and DELETE to enable software applications to exchange structured data and trigger actions, providing the primary integration pattern for modern payment infrastructure platforms.
REST APIs define a set of conventions for how applications communicate over the web. When a platform calls Nium's payment API to initiate a payout, it sends an HTTP POST request to a specific endpoint URL, with a JSON-formatted body containing the payment details and an authentication header proving its identity. Nium processes the request and returns an HTTP response: a JSON object indicating success or failure with relevant details.
The REST architecture's key characteristics make it ideal for payment integration: stateless (each API call contains all necessary information without server-side session state), resource-oriented (each endpoint represents a specific resource, such as payments, cards, or accounts), and HTTP-based (compatible with any programming language or platform).
For payment infrastructure, REST API quality significantly affects the developer experience. Well-designed REST payment APIs use consistent resource naming, standard HTTP status codes for errors, clear JSON schemas with full documentation, and stable versioning policies. Poor API design, with inconsistent naming, unclear error codes, and undocumented fields, creates integration friction and ongoing maintenance burden.
REST APIs are the universal language of modern web services. Any programming language, platform, or cloud infrastructure can make HTTP requests, which makes REST APIs inherently interoperable. For payment infrastructure, REST API adoption means businesses can integrate payment capabilities in their preferred development environment without proprietary tooling or language-specific constraints.
- API documentation must be comprehensive and current: undocumented fields create integration confusion
- Error handling requires developers to map API error codes to business logic responses
- Rate limiting requires retry logic and backoff strategies
- Security requirements for payment APIs require careful credential management
- Breaking API changes in new versions require careful upgrade management
A regional bank integrating Nium's cross-border payment capabilities uses the REST API to connect its existing core banking system to Nium's infrastructure. The bank's Java-based platform sends HTTP POST requests to Nium's payment API, with no proprietary middleware or custom protocol adaptation required. Integration is complete in 8 weeks, ahead of the 14-week estimate using the previous SWIFT-based integration approach.
Related Concepts
All Nium capabilities, including payouts, card issuing, accounts, FX, and compliance, are exposed through a unified REST API. Nium's API is designed for production-grade integration, with comprehensive documentation, consistent versioning, and sandbox availability for pre-production testing.
Answers you didn't know you needed.
What does REST stand for?
REST stands for Representational State Transfer, an architectural style for distributed systems. RESTful APIs implement this style using HTTP as the transport protocol.
What is a JSON payload in a REST API?
JSON (JavaScript Object Notation) is the data format used in REST API requests and responses. Payment details, card credentials, and account information are structured as JSON objects.
What are HTTP status codes?
HTTP status codes are standardized 3-digit response codes indicating the result of an API call. Common codes: 200 (success), 201 (created), 400 (bad request), 401 (unauthorized), 404 (not found), 500 (server error).
What is the difference between REST and SOAP APIs?
SOAP is an older, XML-based messaging protocol used in legacy banking systems. REST uses lighter-weight JSON and standard HTTP, which makes it faster to integrate and better suited to modern cloud infrastructure.
How does Nium version its REST API?
Nium maintains versioned API endpoints, allowing clients to continue using existing integrations while new capabilities are added. Nium provides advance notice of breaking changes and deprecation timelines to enable planned upgrades.