WhatsApp greys out the send button when the message field contains only spaces. Copy this character to keep the button active and send a blank bubble or status.
One character. The bubble is as small as a message can get.
Twenty characters. Produces a visible rectangular gap in the chat.
One hundred characters. A tall empty bubble that fills much of the screen.
Opens WhatsApp with the character already in the message field. You still choose the chat and press send.
Before enabling send, WhatsApp checks whether the message has any content after trimming. An ordinary space (U+0020) is trimmed away, so the message counts as empty and the button stays inactive.
Hangul Filler (U+3164) is not affected by that check. WhatsApp reads it as text and enables send, while the delivered bubble shows nothing.
