Click to chat - Simplest

It's an app to open WhatsApp chat without creating the contact.

This app is not affiliated with nor endorsed by WhatsApp Inc.

You can open a chat in WhatsApp with any number without saving first into contacts by opening in your browser the link 'wa.me/123456789' (using the prefix+number desired)?

Source: https://faq.whatsapp.com/en/android/26000030/

No ads, no data storing and sending