The WhatsApp 24-Hour Window: What You Can and Can't Send

The most common support ticket we see about the WhatsApp Business API goes like this: 'Messages worked yesterday, today they fail.' Nothing broke. The customer's 24-hour window closed, and the software tried to send a plain message into a closed window.

Once you understand that one rule, a lot of API behaviour makes sense. So let us walk through it with a made-up but ordinary example.

The rule in one paragraph

When a customer sends your business number a message, a window opens. For the next 24 hours you can reply with free-form messages: any text, images, documents, whatever fits. Every new message from the customer restarts the clock. When 24 hours pass with no message from them, the window closes. After that, the only thing you can send is an approved message template. If you want the exact current wording and any exceptions, read Meta's own documentation, since policies shift.

A day in the life of one conversation

1. 1Monday 10:00 am. A customer writes to a furniture shop: 'Is the teak shelf in stock?' The window opens.
2. 2Monday 10:15 am. You reply with photos and a price. Free-form is fine.
3. 3Monday 6:00 pm. The customer says they will think about it. The clock restarts from this message.
4. 4Tuesday 7:00 pm. You send a follow-up with a delivery offer. Still inside 24 hours of their last message, so it goes through.
5. 5Thursday 11:00 am. You try to send another nudge. The window is closed. A free-form message fails, and only an approved template can reach them now.

Notice that your own messages never extend the window. Only the customer's replies do. That surprises people who assume that being active keeps the door open.

What a template is, and why it exists

A template is a message you write in advance and submit to Meta for approval. It can have placeholders for a name, an order number or a date. Once approved, you can use it to start a conversation, or to reach someone whose window has closed. Meta's idea is that businesses should not be able to cold-message people with whatever they like, so the pre-approved structure acts as a filter.

Writing templates that get approved is its own skill. We cover the common reasons for rejection in our template approval tips.

What this means for your workflows

• Support replies: Answer inside the window and you are free to write naturally. Slow replies are the real danger, because a ticket that sits for two days has no window left.
• Order updates: If the customer never messaged you, you need a template for the confirmation anyway. Plan the wording ahead.
• Reminders: Appointment and payment reminders usually go to people who have not written recently, so they are template territory.
• Promotions: Always templates, and only to people who agreed to hear from you. See our piece on collecting opt-in.

How a gateway should handle it

Doing this by hand is a recipe for errors, because someone has to remember when each conversation's clock started. A decent system tracks it for you. In the Meta CRM inside WA Getway, the 24-hour window is handled automatically: the inbox knows whether a contact is inside the window, and templates are synced from Meta so your team can pick an approved one when the window is closed.

This is also why campaigns need care. A campaign is, by nature, a message to people who probably have not written recently, so it runs on templates and goes only to opted-in contacts. STOP and START replies are processed automatically, which keeps you on the right side of consent. We go through that side separately in handling STOP and unsubscribe requests.

If you are on a QR connection

The 24-hour rule is part of the official API. A QR-based session does not enforce it in the same way, which is exactly why people are tempted by it. Do not read that as freedom. Messaging people who have not spoken to you is the quickest route to spam reports, and we explain the trade-offs in Meta Cloud API vs QR gateway.

A simple habit that prevents most failures

Before you design any automated message, ask one thing: will the customer have written to us in the last day? If yes, free-form is fine. If no, write and submit a template first. That single question will save you from most 'it worked yesterday' messages.

If you want help mapping your own flows to windows and templates, or wiring this into an existing system, that is the sort of work we do under our services.