# The WhatsApp 24-hour window — what every messaging engineer should know

> Meta's customer-service window changes the economics of WhatsApp Business. Here's how to architect around it for OTPs, support, and post-purchase notifications.

- Canonical URL: https://www.broadnet.me/blog/whatsapp-24-hour-window-deep-dive
- Language: en
- Last updated: 2026-10-10
- Publisher: BroadNet (https://www.broadnet.me)

- Published: 2026-03-28
- Author: BroadNet Editorial Team

WhatsApp Business pricing has been per delivered template message since 1 July 2025 — and what you pay depends on the template category and whether the customer's 24-hour window is open. The most important concept: the 24-hour customer-service window. Get this right and your WhatsApp implementation costs are predictable; get it wrong and you'll burn through Marketing-category templates while customers are actually engaging with you for free.

## How the window works

When a customer sends a message to your WhatsApp Business number, you can reply with Service-category messages for the next 24 hours — billed per message since 1 October 2026 after a free tier of 1,000 service messages per business phone number per month (free until 30 September 2026). After 24 hours of customer silence, the window closes. To re-initiate, you must use a pre-approved template — billed per delivered message as Marketing, Utility or Authentication depending on category.

## What this means for architecture

- Maintain a per-MSISDN window-timer in your system — or use BroadNet's, which is automatic.
- For customer-initiated workflows (support, claims, product Q&A), do everything inside the 24-hour window if you can.
- For business-initiated workflows (delivery notifications, OTPs), choose the lowest-cost template category that fits.
- Template variables save you template-approval cycles. Plan your templates around variable substitution from the start.

## Free allowances Meta offers

Meta keeps two free allowances: the free entry point window (when a customer starts the chat from a Click-to-WhatsApp ad on Facebook or Instagram and you reply within the customer service window, a window opens that can stay open for up to 7 days, with no charge for marketing, utility, authentication or service messages) and, since 1 October 2026, a free tier of 1,000 service messages per business phone number per month, which resets monthly and does not roll over. BroadNet's billing reflects both — you only pay for messages that fall outside them.