API – Application Programming Interface
An API (Application Programming Interface) is a programming interface through which software systems exchange data and call each other's functions. In an ERP context, APIs are the standard way to connect an ERP system with shop systems, integration platforms, banking links, logistics providers or in-house applications.
What an API actually does
An API defines what a system offers without exposing how it works internally. In practice it specifies:
- Endpoints – URLs that expose specific operations (
/customers,/orders) - Methods – read, create, update and delete operations (GET, POST, PUT, DELETE in REST)
- Data format – JSON or XML as the exchange format
- Authentication – API keys, OAuth2 or client certificates
- Versioning – stable contracts so integrations keep working for years
API types in the ERP context
- REST/HTTP APIs – today's standard: lightweight, JSON-based, easy to document via OpenAPI/Swagger
- SOAP web services – XML-based and more formal; still common in legacy ERP systems
- OData – a standardised REST extension with query capabilities
- GraphQL – the client chooses which fields are returned; still rare in the ERP mid-market
- Webhooks – a push mechanism: the ERP calls an external URL when an event occurs (e.g. a new order), ideal for real-time integration
- EDI and file interfaces – CSV, XML, EDIFACT: technically not APIs, but the practical predecessor
What is an API-first ERP?
An API-first ERP exposes every function as an API first, before any user interface is built on top. That makes integrations, automation and custom front-ends far easier – often via middleware or an integration platform. For modern, multi-channel businesses a well-documented, stable API is one of the most important ERP selection criteria.