How fast do messages go out?

Slowly, on purpose. A number that suddenly sends a lot of messages is the quickest way to have it blocked by WhatsApp, so messages from your number go out a few minutes apart, and only in the daytime.

• The first reply to somebody who has just written to you goes straight away.
• Follow-ups, reminders and greetings go on their day, in the daytime. See When are automatic messages sent?.
• A message to everyone goes out a few people at a time, so a large send can take a while to finish.

Waiting to go out on each tab shows how many are still to go. What has been sent shows what has gone. See What has been sent.