The WhatsApp 24-hour window (also called the customer service window) is the period during which a business can send free-form messages to a user on WhatsApp Business API. The window opens when the user sends a message to the business and lasts 24 hours from the user's last message. Outside this window, the business can only send pre-approved template messages.
This rule shapes every WhatsApp marketing funnel, so here is exactly how it works, what resets it, and how to design around it.
How the window works
When a user messages your business — including by tapping a click-to-WhatsApp link or ad — a 24-hour session opens. During the session:
- The business can send any message type: free text, media, interactive buttons, lists.
- No template approval is needed.
- Every new message from the user resets the 24-hour countdown.
When 24 hours pass without a user message, the session closes. From that point, the business can only initiate contact with template messages: pre-written messages submitted to and approved by Meta, organized by category (utility, authentication, marketing).
Why the rule exists
The window exists to prevent spam. WhatsApp's core asset is that users treat it as a personal channel, so Meta enforces a simple principle: businesses can talk freely when the user has invited the conversation (inbound), and only in controlled, pre-approved ways when the user hasn't (outbound). This is also why inbound-first funnels — where the user initiates contact — are structurally safer and cheaper than outbound campaigns.
What opens (and resets) the window
| Event | Effect |
|---|---|
| User sends any message | Opens/resets the 24h window |
| User taps a click-to-WhatsApp ad or link and sends the pre-filled message | Opens the window (counts as user-initiated) |
| User clicks a button inside a message | Resets the window |
| Business sends a message | Does NOT extend the window |
| 24h pass without user activity | Window closes; templates only |
Practical implication: the timer runs from the user's last message, not yours. A common mistake is assuming a long back-and-forth keeps the session alive — it does only as long as the user keeps replying.
Template messages: the rules after the window closes
To message a user outside the window, you must use a template that Meta has approved. Key facts:
- Categories. Templates are classified as utility (order updates, reminders), authentication (codes), or marketing (promotions, re-engagement). Marketing templates face the strictest review and the highest per-message pricing.
- Approval. Templates are submitted through the WhatsApp Business Platform and reviewed by Meta. Approval usually takes from minutes to 48 hours.
- Opt-in. You must have the user's prior opt-in to send template messages. Messaging users who never consented is the fastest route to quality-rating drops and number bans.
- Pricing. Template conversations are billed per conversation by category and country; pricing changes periodically, so check Meta's current rate card.
Designing a funnel around the window
The window rewards funnels where the user initiates and stays engaged. A pattern that works:
- Inbound entry. The user arrives from content or a landing page and taps click-to-WhatsApp. The window opens — user-initiated, fully compliant.
- Contextual first response. Because you know what content or page brought the user, the first message can reference it directly, raising response rates and keeping the session alive.
- Engineered re-engagement. If you plan to recontact users days later (for example, inviting a customer to create content or use a promotion), prepare and pre-approve the templates for that step in advance. Re-engagement outside the window is possible — but only through templates, so design the message flow before you need it.
The mistake to avoid: building a funnel that assumes free-form messaging at day 3 or day 7. Once the window closes, improvisation is off the table; everything outbound must already exist as an approved template.