The WhatsApp customer service window is a 24-hour timer that starts when a customer messages or calls your business number, and resets each time they do it again. While it is open you can send free-form replies such as text, images and documents. After it closes, the WhatsApp Business API only lets you send pre-approved template messages.
The 24-hour customer service window is the rule that decides what you can send on the WhatsApp Business API, and since October 2026 it also affects a lot of what you pay. Meta's documentation describes it simply: when a WhatsApp user messages or calls your business, a 24-hour timer starts. If they message or call again before it runs out, the timer resets to 24 hours.
Inside vs outside the window
| Window open | Window closed | |
|---|---|---|
| What you can send | Any service message: text, images, video, audio, documents, location, contacts, buttons, lists, Flows | Only pre-approved template messages |
| Meta approval needed | No | Yes, for each template before first use |
| Typical use | Answering questions, sending a quote or brochure, booking a visit | First contact, reminders, offers, OTPs, restarting a closed chat |
| Cost | First 1,000 service messages per number per month free, then charged | Marketing, utility or authentication rate |
Either way, you may only message people who have opted in to hear from your business. The window does not replace consent.
Rules people often get wrong
- It runs from the customer's last message or call, not from your reply. Your own messages do not reset it.
- It is per business and customer, so it does not matter which agent or tool sends the reply.
- Not everything inside it is free. Since 1 October 2026, Meta charges for service messages after the first 1,000 per business number each month, and for utility templates sent inside an open window.
- Ad chats can be free for longer. If someone messages you from a Click-to-WhatsApp ad on Android or iOS and you reply within 24 hours, your reply opens a free entry point window. Meta says it may stay open for up to 7 days, and all messages in it are free.
How to use the window well
- Reply fast. A reply inside the window can be a normal typed message. After it closes you need a template, which costs more and may count as marketing.
- End your reply with a question, such as "Shall I hold Saturday 11 am for you?". A customer reply reopens the window.
- Keep approved templates ready for follow-ups after the window closes.
- Do not send a template inside an open window when a free-form reply will do.
How salestrack helps
The salestrack shared inbox shows a 24-hour window timer on every chat, with approved templates ready for when a window closes. Leads from Click-to-WhatsApp ads are given an owner by lead assignment rules, so the first reply is not missed. The help guide The 24-hour reply window and templates shows how it looks in the app.
Related questions
Can I send a free-form message after the 24-hour window closes?
No. Once the window has closed you must send an approved template message. If the customer replies to it, a new 24-hour window opens and free-form replies are allowed again.
Does my own message reset the 24-hour window?
No. Only a message or call from the customer starts or resets the window. Your outgoing messages do not extend it.
Are messages inside the 24-hour window free?
Not all of them. Each business number gets 1,000 free service messages a month; after that, from 1 October 2026, service replies are charged. Utility templates sent inside an open window are also charged since 1 October 2026.
What is a WhatsApp session message?
It is an older name for a free-form reply sent inside the 24-hour window. Meta now calls these service messages.
Does the 24-hour window apply to the WhatsApp Business app?
The customer service window is a WhatsApp Business Platform (API) rule. In the WhatsApp Business app you type messages from the phone, and the API window rules do not apply to app messages.
Sources
Checked on 1 November 2026. WhatsApp and Meta change their rules and prices often, so check the source before you rely on a detail.