API integration is how your separate business systems — your store, CRM, accounting, ERP, payments, shipping — talk to each other automatically, instead of someone copying data between them by hand. A single, well-defined integration typically costs €1,500–€6,000 to build, removes the manual re-entry that wastes hours and causes errors, and keeps the same data consistent everywhere. It’s the plumbing that turns a pile of disconnected tools into one system that works together.
What are API integration services?
Most businesses run on several pieces of software that were never designed to work together: an online store here, accounting there, a CRM, a spreadsheet, a payment provider. An API is the interface a piece of software exposes so other software can read and write its data. API integration services use those interfaces to connect your systems so data flows between them automatically — a sale creates an invoice, a form fills your CRM, stock updates everywhere at once — with no one exporting a CSV and importing it somewhere else.
Signs you need an integration
You probably need one if any of these sound familiar:
- Someone re-types or exports data from one system into another as a routine job.
- The same figure is different in two tools because a manual update got missed.
- A process stalls waiting on a copy-paste step before the next thing can happen.
- You’re paying people to be human glue between software that should talk on its own.
Each of these is both a time cost and an error cost — and both disappear once the systems are connected properly.
Common business integrations
| Integration | What it does |
|---|---|
| Store → accounting | A sale creates the invoice and updates the books automatically |
| Store/ERP → stock | One source of truth for inventory across every channel |
| Forms/WhatsApp → CRM | Enquiries become contacts and trigger follow-up |
| CRM → email/SMS | The right message goes out on the right trigger |
| Payments → systems | Stripe or a gateway keeps orders, invoices and access in sync |
| Shipping → orders | Labels, tracking and status update without manual steps |
Off-the-shelf connectors vs custom API integration
For simple, standard links between popular tools, off-the-shelf connectors — Zapier, Make, or a built-in native integration — are genuinely the right choice and the fastest way to start. Reach for custom API integration when the connector hits a wall: the logic is specific to your business, the volume makes per-task pricing painful, a system you use isn’t supported, or the data needs real transformation the connector can’t handle. In practice many businesses use both — connectors for the trivial links and custom work for the integrations the business actually depends on. This is the same trade-off covered in how to automate your business, because integration and automation are two sides of the same job.
How much does an API integration cost?
A single, well-defined integration between two systems is typically €1,500–€6,000 to build. What moves the number is the quality of the two APIs and how messy the data is: two modern systems with clean APIs are quick; a legacy system with a poor or missing API is where the work goes. Connecting several systems at once costs more, and running costs are usually just hosting plus any per-call API fees. As always, weigh it against the manual hours it removes and the costly errors it prevents — not the sticker price alone.
An integration has to be kept running
Here’s the part that’s easy to miss: APIs change. Providers ship new versions, deprecate endpoints, tighten rate limits and update authentication — and when they do, an integration that isn’t maintained breaks, usually silently, and you find out when data stops matching. So an integration is not a one-off build; like any software that needs maintaining, it needs monitoring and the occasional update. That’s why it’s best built by someone who stays on to run it. Custom API and integration work, built and kept running end to end, is how your systems keep talking long after launch — not just on the day it went live.