WhatsApp 24-hour window: what to do when a customer replies outside business hours

If you're reading this, it's because a customer messaged you at 23:40, or on a Sunday, or while you were asleep, and now you don't know if you can reply or if your response won't go through. It's not a serious error or something you broke: it's how Meta's official WhatsApp API works. The 24-hour window is the period during which you can freely reply to a customer, and it opens with the last message they sent you. When that window closes, the channel isn't blocked: the rule changes. You can keep writing, but only with an approved template, and that's charged as a template conversation. Yes, you can fix it yourself, without relying on support, and in this guide you'll see how.

What the 24-hour window is, in plain terms

Think of it as a counter that opens every time the customer speaks. From that message, and for 24 consecutive hours, you can send them whatever you want: free text, images, audio, documents, whatever you need to help them. It doesn't have to be a formal reply or use a template. It's a normal conversation, and Meta charges it as a service conversation (the price depends on the country; the official values are in Meta's documentation, don't make them up from memory).

The detail most people miss: the window doesn't open when you write, it opens when the customer writes. If you send a message and they don't reply, you don't have a window. And every new message from the customer resets the clock: if they wrote to you on Monday at 10:00 and again on Tuesday at 9:00, you have a window until Wednesday at 9:00. The clock runs from their LAST message, not from the first one.

Why the problem appears right outside business hours

The number one cause is common sense: customers write when they can, not when you're open. A restaurant gets orders at 23:00, a salon gets inquiries on a Saturday afternoon, a real estate agency gets a 'is it still available?' on a Sunday. If your team replies at 9:00 on Monday, between 10 and 14 hours passed in the meantime. And if the customer wrote on Friday and you reply on Monday, more than 60 passed. The window has already closed.

The second cause is not having anyone watching the channel. The official API doesn't forward messages to an email or notify you elsewhere by default: if no one opens the inbox, no one finds out. Many businesses set up the API, connect it, and think that's enough. It's not enough: someone has to see the message within 24 hours.

• The customer wrote at night and the team only saw it the next morning: window expired.
• The customer wrote on Saturday and the team doesn't work weekends: window expired.
• The customer wrote on a long holiday weekend: window expired.
• No one is assigned to the inbox, so the message goes unread: window expired.
• The business did reply, but 26 hours later: the window had already closed and the message went out as a template (or didn't go out at all, depending on the configuration).

How to tell if you still have an open window

Before you write, check the time of the customer's last message. If less than 24 hours have passed, go ahead and write: it's a service conversation. If more have passed, it's no longer open. There's no magic screen that tells you 'window closed' in every panel, so the practical way is this: take the timestamp of the last incoming message and add 24 hours. If that time has already passed, you're out.

Watch out for a technical detail that often confuses anyone looking at databases: the time that counts is the message time according to Meta (the timestamp that comes with the message), not the time your system saved the record. If your panel or your database stores the insertion date (created_at) instead of the message date, any calculation will be wrong. Always use the timestamp that Meta sends.

How to respond when the window has already closed: step by step

1. 1Open the conversation and check the time of the customer's last message. If more than 24 hours have passed, you're already outside the service window.
2. 2Choose an approved template that makes sense for the case. For example, one for 'inquiry follow-up' or 'order reminder'. Don't use a marketing template to answer a specific inquiry: the customer won't understand it.
3. 3Personalize the template variables (name, order number, whatever applies) before sending it. A generic template looks like a robot and lowers response rates.
4. 4Send it and wait. When the customer replies, the 24-hour window reopens and you can continue with free text.
5. 5If the template you need doesn't exist, create it in the WhatsApp Business manager and wait for approval. Meta can take up to 48 hours; there's no way to speed it up.
6. 6If the customer replies and you need a second template because another 24 hours have passed, repeat the cycle. Every customer reply resets the clock.

What NOT to do when the window has closed

• Don't send free-form text messages: they won't go through and you'll waste time thinking the API is broken.
• Don't fire off a marketing template at someone who asked you a question: it's the fastest way to get your number blocked.
• Don't wait for the customer to write back 'just in case': if days have passed, they've probably already bought from someone else.
• Don't use a template without personalized variables: the customer sees it's automated and doesn't respond.
• Don't assume that restarting the integration or reconnecting the number will reopen the window. It doesn't work that way.

How to keep the window from closing before you reply

The real solution isn't technical, it's about process: someone has to see the message within 24 hours. If your business doesn't have people watching WhatsApp at 23:00, you need one of these three things: time-based auto-replies that at least let the customer know you'll contact them, a team that covers shifts, or a tool that helps you not lose the thread.

Time-based auto-replies serve two purposes: they tell the customer their message arrived and that you'll get to it, and they keep the message within the window. Watch out for one detail: the auto-reply doesn't reset the 24-hour window because the window resets with messages from the CUSTOMER, not with yours. What it does do is keep the customer from leaving thinking no one is listening.

If you use Wando, the inbox with AI suggestions shows you unread messages and suggests a reply that you approve with one click. The AI learns from your team's real replies, so the suggestions improve with use. It doesn't reply on its own by default: someone on the team always approves. That helps you lower response time, which is exactly what keeps the window from closing.

When the real problem is something else and the window is just the symptom

There are three situations that look like a 24-hour window problem but aren't. The first: the integration token expired. The symptom is similar (messages don't go out), but the cause is different and it's fixed by reconnecting the account. The second: the template isn't approved or was rejected. The message doesn't go out, but the reason is the template, not the clock. The third: the number is restricted or has a low quality limit. There, messages may go out with a delay or not go out at all, and the problem is the number's reputation, not time.

How do you tell them apart? Look at the specific error the integration or the panel returns. If the error mentions the window or the conversation type, it's this. If it mentions authentication, token or session, it's the token. If it mentions template, it's the template. If it mentions quality or restriction, it's the number. Each one has its own solution path and they don't fix each other.

One last scenario: the customer replies outside business hours, you send the template the next day, and they answer. Perfect, the window is open again. But if your team takes 30 hours to send that template, the customer is already gone. The window is a technical rule, but the underlying problem is response time. If you want to see how that is solved with an inbox that organizes your messages and suggests replies, you can try Wando free for 14 days, no card required, and see the plans at wando.online/pricing.