Session Message vs Template Message on WhatsApp: The 24-Hour Rule Explained

Everyone who starts using the WhatsApp Business API runs into the same moment: an agent types a reply to a customer, presses send — and the panel says a template is required. Yesterday the same chat worked fine. The reason is the difference between a session message and a template message, and the 24-hour rule that decides which one you are allowed to send.

WhatsApp Business API session message vs template message

“Session message” is the name most providers use. Meta's own documentation calls these service messages or non-template messages. They mean the same thing.

How the 24-hour customer service window works

When a customer sends you a message, a customer service window opens for 24 hours. While it is open, you can send any kind of message: free text, photos, PDFs, voice notes, interactive buttons. Every new message from the customer restarts the 24 hours.

Once 24 hours pass with nothing from the customer, the window closes. From then on, you can only reach that customer with an approved template — until they reply again, which opens a fresh window.

A worked example

1. Monday 10:00 — A customer messages your clinic: “Do you have a slot on Thursday?” A window opens until Tuesday 10:00.
2. Monday 10:05 — Your receptionist replies with available times. Session message.
3. Monday 18:30 — The customer replies “4 pm please.” The window now runs until Tuesday 18:30.
4. Wednesday 09:00 — You want to send a reminder. The window closed on Tuesday evening, so this must be a template, such as an appointment reminder.
5. Wednesday 09:20 — The customer taps “Confirm” on the template. That is a message from them, so a new window opens and your team can chat freely again.

When a template is required

You need an approved template whenever there is no open window:

• Messaging a customer first — they have never written to you, or not in the last 24 hours.
• Broadcasts — offers and announcements to a list, since most recipients will not have an open window.
• Follow-ups after a quiet day — a quote reminder, a “did you get a chance to look?”, a payment reminder.
• Automated notifications — order confirmations, shipping updates, appointment reminders sent from a system.
• One-time passwords — these always use an authentication template.

Templates also count toward your messaging limit — the number of unique customers you can reach outside the window in 24 hours. Session messages do not. For how templates are built and approved, see WhatsApp message templates.

The 72-hour exception: ads and Page buttons

If a customer messages you from a Click-to-WhatsApp ad or a Facebook Page call-to-action button, Meta opens a free entry point window: messages you send in the following 72 hours are free, templates included. The 24-hour rule for what you may send still applies to free-form messages; the 72 hours is about what you are charged.

What changes on 1 October 2026

Until now, the practical difference in cost was simple: session messages were free, templates were paid. From 1 October 2026, that changes. Meta's rate card effective 1 October 2026 adds a service rate for every market, equal to that market's utility rate — for India, ₹0.115 per delivered message, before GST. Utility templates sent inside an open window also stop being free.

Meta's partners report a free allowance of 1,000 service messages per business phone number per month. When we checked on 14 September 2026, that allowance was not written on Meta's own pricing pages, so treat it as announced to partners until Meta publishes the final terms. Our full breakdown, with worked bills for Indian businesses, is in WhatsApp pricing change on 1 October 2026.

Common mistakes with the 24-hour rule

• Counting 24 hours from your last message. The window runs from the customer's last message. Your own replies do not extend it.
• Treating a delivered template as an open window. Sending a template does not open a window; only a reply from the customer does.
• Reaching for a marketing template by habit. A follow-up that is purely about the customer's own order or booking, with no offer in it, can be a utility template — at a fraction of the price.
• Letting a chatbot hold the conversation too long. A bot that asks five questions one at a time sends five session messages; from October, each one is charged.

Using the window well

1. Reply fast. A customer who writes at 9 p.m. and gets an answer at 10 a.m. is still inside the window; one who gets an answer two days later needs a template.
2. Answer in one complete message. From October each session message is charged, and one clear reply beats four short ones.
3. Ask a question that invites a reply. Every customer reply restarts the 24 hours, so a conversation that keeps moving never needs a template.
4. Keep a few follow-up templates ready — a quote reminder, a “we tried to reach you”, a feedback request — for chats that went quiet.
5. Use buttons on templates. A quick-reply tap reopens the window without the customer having to type.

How wbm.link handles the window

In the wbm.link team inbox, your team replies freely while a conversation's window is open, and the reply box warns when it is about to close. Once it has closed, the box locks and offers Send template instead, so nobody sends a message that WhatsApp would refuse. Session replies and templates are billed from the same prepaid wallet, and the platform fee stays ₹999 per connected number per month, with unlimited team members.