Head Shaking Horizontally

Usually a soft, polite no. The smile keeps refusal or disagreement friendly: low-stakes pushback, not an eye-roll. Emoji 15.1 built it by joining a slightly smiling face 🙂 to a left-right arrow ↔️ with an invisible joining character. The gesture itself is old; Charles Darwin suggested in 1872 that babies turning away from unwanted food may have shaped the refusal shake, though that remains a theory.

The Unicode proposal named the motion rather than calling it “no”, because head gestures don't mean the same thing everywhere. The smile is there as a generic face, not as a sign of happiness.

Does a head shake always mean no?

No, not everywhere. In Bulgarian convention, a side-to-side movement can signal yes and a nod can signal no. If you don't know which convention the sender follows, let the surrounding words decide, or simply ask.

What should I read when someone sends this?

Usually a gentle decline; check the words around it. On its own it says no without explaining why. Inside a longer message it colours the text rather than answering anything. The smile tells you the sender is keeping things friendly, so it rarely signals anger.