WhatsApp is one of the most used messaging apps in the world, and many people would rather message a business than call it or open an email. The WhatsApp Business API is how companies meet them there — sending order updates, appointment reminders, support replies and more, from their own software and at scale. This guide explains what it is, how it differs from the apps you already know, and what you need to start.

The WhatsApp Business API, in one sentence

It is an interface, provided by Meta, that lets your software send and receive WhatsApp messages through a business number — no phone in someone's hand required. Where the consumer app and the WhatsApp Business app are built for a human tapping the screen, the API is built for systems: your website, your CRM, your order pipeline, your helpdesk.

Cloud API — the only version today

Meta hosts the Cloud API: you call its endpoints, it runs the infrastructure, and calling the API itself is free (you pay for messaging, more on that below). The older On-Premises API, which businesses hosted themselves, has been retired — its final version expired on 23 October 2025. Modern providers, walpio included, build on the Cloud API. More in the On-Premises sunset.

What you can do with it

  • Send notifications — order confirmations, shipping updates, reminders, one-time codes.
  • Have conversations — receive inbound messages and reply, from a team inbox or automatically.
  • Broadcast — send an approved template to many opted-in customers at once.
  • Track delivery — see sent, delivered, read and failed status for every message.

The rules that trip everyone up

WhatsApp is not email — you cannot message anyone you like, whenever you like. Three rules matter most:

  • Opt-in first. You may only message people who gave you their number and agreed to hear from your business on WhatsApp — see opt-in and opt-out.
  • The 24-hour window. You can send free-form messages only within 24 hours of the customer's last message or call. Outside it, you must use a template Meta has approved. (This is the single biggest source of “why didn't my message arrive?” — see the 24-hour window explained.)
  • Templates are reviewed and categorised. Meta reviews every template and decides its category — marketing, utility or authentication — which sets its price. See how templates get approved.

What does it cost?

Calling the API is free; Meta charges per delivered message, by category and by the recipient's country. Marketing templates always cost the most. From 1 October 2026, utility templates are charged even inside the 24-hour window, and your free-form replies in the window are free only for the first 1,000 per number each month — after that Meta charges the utility rate. A provider on top typically adds a subscription for the software layer. The full picture is in how WhatsApp Business API pricing works — and walpio never marks up your Meta traffic.

What you need to get started

  1. A Meta business portfolio. Business verification is worth doing early: it raises how many customers you can message per day.
  2. A phone number you control that can receive Meta's verification code.
  3. A display name and at least one approved message template.
  4. A way to actually call the API — either build directly against Meta, or use a gateway that handles the hard parts for you.

That last point is where most of the work hides. The window logic, choosing the right template, webhook signature verification and delivery tracking are all things you can build — or skip. That is exactly what walpio does: you bring your own Meta number, and we operate it behind one send endpoint whose body follows the Cloud API's text and template shapes.