Every message sent through the WhatsApp API goes through one of four possible states. Here is what each one means.

Sent

Your message has left WhatsApp's servers, but it hasn't reached the recipient's device yet.

Delivered

The message has successfully reached the user's device and is available in their WhatsApp.

Read (blue)

The user has opened the chat and seen your message. This status is only available if the user has enabled read receipts.

Failed

The message could not be delivered. Common reasons include an invalid phone number, the user blocking your business, or the message not complying with WhatsApp's policies.

Meta charges only for messages that reach the Delivered status. Messages that remain in Sent or end up as Failed are not billed.