How to write short birthday wishes
Short messages work because they leave no room for filler. Pick one strong idea, like a wish, a compliment or a joke, and say it in a single breath. If it still feels a bit bare, add the person's name at the start or an emoji at the end; that's usually all a short message needs.
A short line is also a great starting point. Copy one here, then add a single detail only you could know, like a place, a habit or an inside joke. You'll still be under two sentences, and it will sound completely like you.