How to send an invisible/blank/empty Whatsapp message?

WhatsApp does not allow you to send a invisible/blank/empty message using regular spaces. To work around this problem, you have to use a different character that looks like a space, but is not recognized as a space by WhatsApp. Such a character is the Unicode character U+3164 HANGUL FILLER, which you can copy to your clipboard using the following "Copy" button:

After copying the character, you can paste it into your WhatsApp message.