Quick answer
Te extraño
the everyday version
Te echo de menos
the alternative — see below for when
Which one to use
Both are understood everywhere, so neither is a mistake. But they are not interchangeable in sound: te extraño in Madrid sounds faintly Latin American, and te echo de menos in Mexico City sounds faintly Spanish. Pick the one for the country you care about.
Extrañar comes from “to find strange” — you miss someone because their absence feels wrong. Echar de menos is literally “to throw of less”. Learn them as blocks, not as parts.
All the versions
Te extraño.I miss you. — Latin America
Te echo de menos.I miss you. — Spain
Lo extraño. / La extraño.I miss him. / I miss her.
¿Me extrañas?Do you miss me?
Me haces falta.I need you here. — heavier, more intimate.
Where you are matters
Spain: te echo de menos. Latin America: te extraño. Te añoro exists in both but belongs in a poem.
Check yourself
You are texting a friend in Madrid. The most natural is: