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The 24-hour window

WhatsApp's rule, not ours — and the thing that surprises every integration built on the assumption that you can message anyone at any time.

A business may send a customer whatever it likes for twenty-four hours after that customer's last message. Outside that window it may send only a template approved by Meta in advance.

Every reply resets the clock. A customer who writes at 09:00 and again at 18:00 can be messaged freely until 18:00 the following day.

Why it decides how your workflows behave

The most valuable follow-up is the one that goes out a day after somebody asked a price and went quiet. That is, by definition, outside the window — so it must be a template, and the template must have been written and approved before you needed it.

This shapes the work in three ways:

• Templates are submitted to Meta and reviewed, which takes anywhere from minutes to a day. Anything a workflow sends after a delay needs one approved before the workflow is useful.
• Templates have fixed text with variable slots. You fill in the blanks; you do not write the sentence at send time.
• Meta charges per conversation, and a template that reopens a closed window starts one. A duplicate send is a duplicate charge as well as an irritated customer.

What your integration sees

Nothing, most of the time — which is the point. Your code records events; workflows decide whether a moment needs a template, and the send layer refuses anything that would breach the rule.

A refusal is an outcome rather than an error. A workflow that tries to message somebody outside the window without a template does not fail — it records that it was refused and why, and that appears on the workflow run in the dashboard. The same is true for a customer who has unsubscribed or never opted in.

"refused": "This conversation is outside its 24-hour reply window.
             Send an approved template instead."

The practical consequence

When you design a workflow, ask how long after the trigger the message goes out. Under twenty-four hours from the customer's last message, ordinary text works. Longer — and a follow-up is almost always longer — you need an approved template, so write it first.

Getting this backwards is the usual first disappointment: a workflow that tests perfectly against a customer who just messaged, and then silently refuses in production against customers who have not messaged in days.