One of the text reaction buttons on an iPhone

HAHA

This reaction often follows something funny in a message.

On an iPhone, the "HAHA" button is one of the quick reaction options for text messages, alongside others like "Love" or "Thumbs Up." The clue refers to these built-in responses, and "HAHA" is a straightforward answer since it’s a common reaction for something funny. No wordplay is involved—it’s a direct reference to a standard iPhone feature.