WhatsApp Business API 24-hour window: a practical guide

Quick answer: on the official WhatsApp Business API, when a customer messages you, you get 24 hours to chat with them at no cost. Once that window closes, you can only restart the conversation with a Meta-approved message template, and that message is paid. If you plan your follow-ups inside the window and get your templates approved ahead of time, you can migrate without stopping your operation.

If Meta shut down unofficial WhatsApp tomorrow, how long would your operation be down? I ask this in almost every mentoring session, and the answer is almost always an uncomfortable silence.

I think that, in the not-so-distant future, we will all be forced to move to the official API. So the best time to prepare is before you need to. In this article I explain the window rule, the most common mistakes and the step-by-step process I use with my clients.

How the 24-hour window works

The logic is simple once you see the conversation as a window:

The window is closed by default. The customer opens it by sending you a message.
Open window = 24 hours of free conversation. During that time you reply, send audio, links, proposals, with no conversation-opening cost.
Closed window = you need to "knock on the window". You do that with an approved template. If the person replies, the window opens again for another 24 hours.
After sending a template, you wait. Until the person replies, you cannot send another free-form message on top of it.

It doesn't matter if it's an active customer, a list that's already yours or a new contact: if you're the one starting the conversation, you pay for the message.

Why the window changes the way you handle customers

Picture a business that works Monday to Friday. A lead messages on Friday at 7 p.m. The 24 hours run until Saturday night. If nobody replies, on Monday you will need a paid template to pick the conversation back up, and in the meantime the person may have closed with another supplier.

Now, if someone had replied right away, you would have had the whole window to guide the conversation at no extra cost.

Templates: what blocks approval

A template is a standard message that Meta reviews before releasing it. And Meta is strict. I've had a "Good afternoon, so-and-so, how are you?" rejected.

There are different template categories. Marketing ones (re-engagement, offers) tend to be more expensive; operational or utility ones (order confirmation, appointment confirmation) tend to be cheaper. I usually register them as utility, and sometimes Meta itself reclassifies them as marketing. It's worth trying.

What I learned in practice:

Register about two days in advance. The first time you use a template, never leave it for the day you need to send it.
Keep wildcard templates approved. I keep four: good morning, good afternoon, good evening and hello, with the first name as a variable. That way the message goes out personalized and I'm never left without a way in.
Get the whole package approved at once. Not just the conversation-opening message. If something changes on the other side, you are not stuck redoing part of the process.
Organize by phone number. A template is tied to the number it was approved on. Putting the last four digits of the phone number at the start of the template name helps a lot when you have more than one number.
Write the message in the template, not in the flow. I call the template from inside the flow. If I need to edit it, everything is organized in one place.

Step by step to prepare for the migration

This is the checklist I share in my mentoring sessions:

Review your profile name. Meta keeps changing how WhatsApp works, with the idea of usernames, like on Instagram. Get your company name right and avoid emojis.
Duplicate all your bots. Keep a copy of each flow ready to run on the official API. If the switch flips, you just connect it.
Put your follow-ups inside the window. Instead of 24 or 48 hours, schedule them at 2 hours and at 20 hours. I also use 23 hours instead of 48 to give the lead one last chance to message again.
Separate re-warming from re-opening. Re-warming messages go inside the window. Re-opening messages go with a template.
Run a morning "sweep". Every morning, filter who has an open window and hasn't replied, and send a re-warming message. No template needed.
Set up WhatsApp payment. It's a separate setup inside the WhatsApp options. Your ad account card doesn't count.
Pick the right moment to switch. During the migration the number stays disconnected for a while. I suggest doing it when the business is closed, on a Friday, so you can upload the templates and have everything active on Monday.
Collect phone and email in your forms. If the channel's cost changes, having contact details gives you other routes, like email and SMS.

Where AI fits in

The 24-hour window is exactly why I think AI in customer service has become even more relevant. Leads message you in the middle of the night, on weekends, in the middle of a launch with dozens of people writing at the same time. A human can't reply to everyone inside the window.

AI replies right away and uses the window to drive a conversion. And conversion here isn't just a sale: it can be a booking, a meeting, the next step in the negotiation.

It also helps with re-opening. An automation sends the template at the right time; when the customer replies, the AI steps in and guides the conversation inside the new window.

What about the cost?

There is a cost per message and it changes often, so always check Meta's current pricing. But look at it the right way: if you spend a few reais on messages with a customer and they convert, the sale pays for that investment many times over. If you're spending a lot on sends with no return, the problem probably isn't the channel. It's the list, the approach or the offer.

Frequently asked questions

How long is the WhatsApp Business API customer service window?

24 hours from the customer's last message. Each new message from them renews the window.

Do I need a template to reply to a customer who messaged me?

No. Inside the window you can chat freely. A template is only required to start or restart the conversation after the window has closed.

Why was my WhatsApp template rejected?

The review is strict and sometimes rejects simple messages. Register in advance, keep generic templates approved and test variations.

Can I use my ad account card to pay for WhatsApp messages?

No. WhatsApp payment is set up in a separate place, inside WhatsApp's own settings.

Do I need to migrate to the official WhatsApp API now?

You don't need to shut anything down today. But get everything ready, with duplicated flows and approved templates, so that when the switch comes, it's just a matter of connecting.

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Want help preparing your operation?

If you want to understand how your operation would look on the official API, talk to Aurora, our assistant: talk to Aurora on WhatsApp.

The WhatsApp Business API 24-hour window, explained