If a notification is plain text then it is limited to 1024 characters. If it includes a PDF or images, then it is limited to 160 Characters. The maximum size for media attachments is 100Mb pre-processed.
For messages in a customer care session, the usual WhatsApp character limits of 65K characters apply.
Learn more about how you can use the Sinch WhatsApp Business API to send messages easily and securely.