API stands for Application Programming Interface. In plain terms, it is a defined way for two software systems to communicate and exchange data with each other. When your Shopify store sends an order to Fortnox, that happens through an API. When Fortnox updates a stock level and pushes it to your webshop, that happens through an API too.
How APIs work
An API is a set of rules that defines what requests one system can make to another and what responses it will get back. System A sends a structured request — "create an invoice for this order with these details" — and System B responds with the result — "invoice created, here is the ID."
You don't need to understand the technical details of how APIs are built to use them. What matters is knowing that APIs are what makes integration possible: they are the communication channel that allows systems to share data without a human copying it from one screen to another.
APIs in ecommerce
Most modern ecommerce platforms and ERP systems expose APIs. Shopify has an API. Fortnox has an API. Visma, Business Central, Klarna, Stripe, and nShift all have APIs. These APIs are what allow an integration platform like Junipeer to connect them.
When you configure a flow in Junipeer — for example, "create a Fortnox invoice for every Shopify order" — Junipeer uses Shopify's API to read the order data and Fortnox's API to create the invoice. You configure what data maps to what field. Junipeer handles the API calls.
API authentication
APIs are not open to anyone. Systems require authentication before they allow other systems to read or write data. Common methods include API keys, OAuth tokens, and username and password credentials. When you connect a system to Junipeer, you are providing the credentials that allow Junipeer to make authenticated API calls on your behalf.
Without APIs: manual work
Before APIs were common, moving data between systems meant exporting a file from one system and importing it into another. The limitations are significant: data is only as current as the last export, errors introduced during import are hard to trace, and the process requires someone to run it manually.
APIs enable real-time or near-real-time data exchange, automatic error handling, and per-transaction logging that tells you exactly what happened to each order.
Next steps
What is iPaaS? | Integration platform for ecommerce | All integrations