What is the WhatsApp 24-hour window?
The 24-hour window is the period after a customer messages your business during which you can reply with free-form messages. It opens each time the customer sends you a message and closes 24 hours after their most recent one. Outside it, you can only send a template Meta has approved.
What opens the window
Only an inbound message from the customer. Your own messages do not extend it — replying at hour 23 does not buy you another 24 hours.
Each new inbound message resets the clock to a fresh 24 hours from that message.
What you can send inside it
Anything: free-form text, images, documents, audio, and templates if you want them.
What you can send outside it
Only a template that Meta has approved in advance. A free-form message sent outside the window is rejected by the API — the customer never receives it.
This is why businesses keep a small set of approved templates for re-engagement: they are the only way to restart a conversation that has gone quiet.
Why it exists
It is the mechanism that stops WhatsApp becoming a cold-outreach channel. Free-form messaging is reserved for conversations the customer started, which is what keeps inboxes worth opening.
PingPlug shows the remaining window on every conversation as a live countdown, and switches the composer to templates once it closes — so a reply is never written and then rejected.