WhatsApp 24-Hour Window: How It Works and When It Closes

The "24-hour window" is the rule that confuses business owners the most on WhatsApp, and it quietly decides what you can send and what you pay. Once you picture it as a timer, the whole thing gets simple.

The quick answer: when a customer messages your business, a 24-hour timer starts. While it is running, you can reply with normal messages. Since October 1, 2026, Meta charges for each delivered reply once your business phone number has used its 1,000 free service messages of the month. When the timer runs out, you can no longer send a free-form message. To reach that person again you need a pre-approved template, which usually costs money. Only the customer's reply restarts the timer.

What the window is

WhatsApp protects people from business spam, so it does not let you message anyone, anytime. Instead it gives you a window: a 24-hour period, opened by the customer, during which you can have a normal back-and-forth.

Inside the window you can send free-form messages (text, images, voice notes, answers to questions). Meta calls these service messages. Each business phone number gets 1,000 free service messages per month, and since October 1, 2026, Meta charges for every service message after that. Outside the window, the only thing you can send is an approved message template, and templates also carry a per-message cost.

How it opens, and how it resets

This is the part most explanations skip, and it is the key to everything:

The window opens when the customer messages you. It resets to a fresh 24 hours every time the customer messages again. Your own messages, however many you send, do not extend it. So a window can quietly run out even while you are busy replying, if the customer has gone silent.

An example

Say a customer messages your shop on Monday at 9:00 am:

Time	What happens	Can you message freely?
Mon 9:00	Customer asks "Do you have the blue one in size M?" The 24-hour window opens.	Yes
Mon 9:05	You reply with a photo and the price. This is a service message, and the first 1,000 service messages each month on your number are free.	Yes, inside the window
Mon, rest of day	You answer a couple more questions. The customer goes quiet after noon.	Yes, until Tue 9:00
Tue 8:30	The window is about to close and the customer has not replied.	Yes, but only for 30 more minutes
Tue 9:00	24 hours have passed since their last message. The window closes.	No, you now need a template
Wed	You want to follow up, so you send an approved template (a paid message).	Only via template

The lead was warm on Monday, and you could answer every question with normal replies. Those cost nothing while your number is within its 1,000 free service messages of the month. By Wednesday, reaching the same person costs a template.

The Click-to-WhatsApp ad exception

There is one important exception. When a customer taps a Click-to-WhatsApp ad and messages you from the WhatsApp app on Android or iOS, and you reply within 24 hours, Meta opens a free entry point window. It can stay open for up to 7 days. While it is open, Meta does not charge for the marketing, utility, authentication or service messages you send. The 24-hour rule still decides what you can send. Once the customer has been silent for 24 hours, you need a template, and Meta does not charge for that template while the free entry point window is open. It is one reason ads that open a WhatsApp chat work well. You get up to 7 days of free messaging to convert the lead.

Why it matters

The window quietly controls what you are allowed to send and what you pay. Conversations handled inside the window are natural, and your replies cost nothing until your number has used its 1,000 free service messages of the month. Conversations that lapse force you back to paid templates, with limited, pre-approved wording. So a warm conversation that goes cold can cost you the sale, and your next message to that person has to be a paid template.

Keeping the conversation alive, the right way

Here is the subtle part: because only the customer's reply resets the clock, a promising chat can lapse simply because nobody followed up in time. Your messages do not extend the window, so you cannot just keep it open by talking.

A good API platform helps you avoid that, tastefully. Because an AI agent reads the whole conversation, it can tell when a lead is warm but has gone quiet, and send one genuinely useful, well-timed message before the window closes (at a sensible hour, not the middle of the night) that invites a reply. If the customer answers, the window resets and you can keep replying with normal messages instead of a template.

The key word is useful. This works when the follow-up actually helps the person: a reminder about something they asked to hold, an answer they were waiting on, a gentle nudge with the next step. It does not work as a hollow "just checking in" blast, which annoys people and drags down your quality rating. Done well, it simply means fewer warm conversations slip away, and fewer of them fall back to paid templates.

For the cost side of all this, see how WhatsApp pricing works, and for what you can send when the window is closed, see message templates. New term along the way? The glossary has it.

Common questions

What is the WhatsApp 24-hour window? It is the period after a customer's last message during which your business can reply freely with any message. Outside it, you can only start or restart the conversation with a pre-approved template message.

How does the 24-hour window reset? Only the customer resets it: every new message from them starts a fresh 24 hours. Your own replies do not extend it.

Is there any exception longer than 24 hours? Yes, for what Meta charges. When a customer taps a Click-to-WhatsApp ad and messages you from the WhatsApp app on Android or iOS, and you reply within 24 hours, Meta opens a free entry point window. It can stay open for up to 7 days. While it is open, Meta does not charge for your marketing, utility, authentication or service messages. Free-form messages still need an open 24-hour window.

What can I send after the 24-hour window closes? Only an approved message template, utility or marketing depending on the case. Meta charges for each template it delivers, unless a free entry point window is open. If the customer replies, the window reopens for 24 hours and free-form messages are allowed again.

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Ciarem's AI watches every open window for you, answers in time, and follows up with one well-judged message before a warm conversation lapses. Fewer chats fall back to paid templates, more of them convert, and you can verify it answers correctly first. Let Ciarem handle the timing.