WhatsApp chat API: how two-way conversations work

A chat API lets your software hold a live, two-way conversation with a customer on WhatsApp, rather than just send notifications. On WhatsApp there is no separate product for that. The same Cloud API that sends a template does three things that together make chat:

• Send: text, media, buttons and lists through the messages endpoint.
• Receive: the customer’s messages pushed to your webhook as they arrive.
• Track: sent, delivered and read events for every message you send.

Wire those three to a screen where people can see conversations and reply, and you have a WhatsApp inbox. The rest of this page is the detail. If you are new to the API itself, start with what the WhatsApp API is.

Everything in WhatsApp chat is governed by one rule. When a customer messages you, a 24-hour customer service window opens. Inside it you can send any message type. Each new customer message resets the clock. When it expires, the only thing you can send is an approved template.

In practice: a customer asks “is this in stock?”, you have a day to answer as freely as you like. If you want to follow up next week, that is a template. Templates that pass review are in our gallery.

You never poll for messages. Meta POSTs each one to the webhook URL you registered, signed with your app secret. A text reply looks like this:

{
  "object": "whatsapp_business_account",
  "entry": [{ "changes": [{ "field": "messages", "value": {
    "messaging_product": "whatsapp",
    "contacts": [{ "profile": { "name": "Priya" }, "wa_id": "919876543210" }],
    "messages": [{
      "from": "919876543210",
      "id": "wamid.HBgMOTE5...",
      "timestamp": "1725000000",
      "type": "text",
      "text": { "body": "Is the blue one in stock?" },
      "context": { "id": "wamid.of.the.message.they.replied.to" }
    }]
  }}]}]
}

Three fields matter for chat. from is who to reply to. id is what to dedupe on, since Meta retries. And context, when present, tells you which of your messages they replied to, which is how a button tap or a quoted reply is linked to the right question. Media arrives as an ID you fetch separately. The full flow, with verification code, is in the webhook guide.

Chat on WhatsApp is not only text. Interactive messages turn a question into a tap, which cuts typing on both sides and keeps answers clean enough for software to act on.

A reply-button message

{
  "messaging_product": "whatsapp",
  "to": "919876543210",
  "type": "interactive",
  "interactive": {
    "type": "button",
    "body": { "text": "The blue one is in stock. Want me to reserve it for you?" },
    "action": { "buttons": [
      { "type": "reply", "reply": { "id": "reserve_yes", "title": "Reserve it" } },
      { "type": "reply", "reply": { "id": "reserve_no",  "title": "Just looking" } }
    ] }
  }
}

The tap comes back on the webhook as type: "interactive" with the button id, so your code gets reserve_yes rather than having to parse “yes pls”.

For every message you send, Meta later posts status events: sent, delivered, read, and failed with a reason. Store them against the message ID and your inbox can show ticks like the app does.

You can also mark the customer’s message as read, which shows them blue ticks, and since 2025 you can show a typing indicator while an agent composes a reply. Both go through the messages endpoint:

{
  "messaging_product": "whatsapp",
  "status": "read",
  "message_id": "wamid.HBgMOTE5...",
  "typing_indicator": { "type": "text" }
}

Small things, but they are the difference between a chat that feels live and one that feels like a ticket queue.

The API gives you messages in and messages out. A team needs more than that to answer customers without stepping on each other. This is the layer platforms exist to provide.

Replying inside the window is a service message. Meta has not charged for those since November 2024, and continues not to until 30 September 2026. From 1 October 2026 service messages are billed per message at the utility rate for the country, which for India is ₹0.13 today. Reopening a conversation with a template costs the template’s category rate: ₹0.88 for marketing, ₹0.13 for utility.

Building a chat integration is a weekend if you only need a bot to answer one question. It is months if you need a team to use it every day, because the inbox layer above is where the work is: threads, assignment, media handling, retries, template management, and reporting.

Build it yourself if WhatsApp chat is your product, or if you need the conversation embedded inside a system you already run. Use a platform if your goal is to answer customers well and run campaigns. Either way, register the number to your own WhatsApp Business Account so you can move later.

Boldally Chat is the platform option: the official API, a shared inbox built for Indian teams, and Meta’s message rates with nothing added on top. See what the inbox includes or the pricing.

Message types, limits and pricing are set by Meta and change over time. Verify against Meta for Developers before building on any specific value here.