The 24 hour customer service window, explained
Why your reply sometimes fails to send, what opens the window, what closes it, and the one kind of message that reaches somebody after it has shut.
· 5 min read
Almost everybody who runs support on WhatsApp discovers this rule the same way: a reply that looks like it sent, to a customer who never answers, because it never arrived. The behaviour is deliberate and it is Meta’s, not your provider’s — but a good provider makes it visible rather than letting you find it this way.
What the window is
When a customer messages your business, WhatsApp opens a 24 hour customer service window. Inside it you can reply with anything: free text, images, documents, voice notes, as many messages as the conversation needs. No template, no approval, no charge.
When it closes, free-form messages stop being deliverable. Not delayed — refused. The only thing that reaches that person now is an approved template.
What opens it, and what does not
- A message from the customer opens it, and every further message from them resets the 24 hours from that moment.
- Your own messages do not. Replying does not extend the window; only they can do that.
- Tapping a button on your template counts as a message from them, which is why a quick-reply button is a useful thing to put on a template even when you do not need the answer.
Reaching somebody after it closes
One thing works: an approved template. Templates exist precisely to be the way a business starts a conversation, so they reach anybody regardless of any window — and sending one opens a new one.
That is the whole design. Free-form messaging is reserved for conversations the customer started, and anything you initiate goes through copy Meta has reviewed. It is a spam control, and it is the reason WhatsApp open rates are what they are.
A template can carry an image, a video or a document in its header, so “send them the invoice” is still available after the window shuts — it just travels as a template rather than as a bare file. See templates for how the categories work.
What this means for a support team
Three practical consequences, in the order they will bite:
- Answer inside the window and it is free. Meta stopped charging for service messages in July 2025. A team that replies a lot is not a team that costs more — provided your provider passed that on.
- Overnight is where threads die. A message at 11pm answered at 10am the next day is fine. The same message answered two days later needs a template, and the customer has usually gone elsewhere by then.
- Keep a template for closed windows.One approved utility template that says “we replied to your question, tap to continue” turns a dead thread into a live one, because their tap reopens the window.
How Sendrix shows it
The window is on the thread in the inbox, counting down, rather than being something you discover by sending into silence. When it has closed the composer says so and offers the approved templates that will still reach that person. The API behaves the same way: a bare file sent to somebody outside their window is refused up front with a specific error code rather than accepted, charged for, and dropped.