What to text instead of “happy birthday”
“Happy birthday!” is fine the way a paper napkin is fine. It does the job and nobody remembers it.
The alternative is not a longer message. It is a more specific one.
Name the detail
“Still think about the time you drove four hours to sit in a hospital waiting room with me.” That sentence is worth two hundred cake emojis.
Say the thing you assume they know
Most people do not actually know how they land on others. Tell them plainly: you are the person I call first, you made this year survivable, you are funnier than everyone you are related to.
Keep it short enough to read on a lock screen
One or two sentences beats a paragraph, especially when their phone is receiving fifty other messages in the same minute.