Direct Message is app to send whatsapp without saving number. User can instang message in whatsApp without adding number.

In WhatsApp send message without adding contact android?
Yes using Derect Message or Instant Messenger user can send message without adding contact.

how can send message to whatsapp without adding contact?
1. Enter a number or copy paste from call logs to which you are going to send message.
2. Enter text message which you want to send.
3. Tap on send button to open official WhatsApp app.
4. This will take you to the official WhatsApp app then a chat window is created with given number.
5. Your chat is started. Use all WhatsApp features for messaging and sending media files.

What is Direct Message?
It is rather inconvenient to add someone to your contacts, only to send them a single WhatsApp/Telegram text. Direct Message allows you to send WhatsApp/Telegram messages directly to the phone number, without saving it to your contacts.

Just select the appropriate country code, enter the receiver's phone number and the text message that you want to send, then click on the Send button. You will be redirected to the WhatsApp chat for that number, even though the contact is not saved on your device.

Note: The entered phone number should already be registered on WhatsApp, otherwise the message won't be received.

Disclaimer
Direct Message application is using official public API available from your WhatsApp app. This app is not associated with WhatsApp. WhatsApp is a registered trademark of WhatsApp Inc. You should follow WhatsApp's terms & condition while sending messages through WhatsDirect App. Any unauthorized downloading or re-uploading of contents and/or violations of Intellectual property rights is the sole responsibility of the user.