Questions & Answers about Alguien está en la puerta.
Both are correct, but they’re used a bit differently.
- Hay alguien en la puerta is the most idiomatic way to announce an unknown presence at the door. It introduces the existence of “someone.”
- Alguien está en la puerta is also fine, but it sounds more like you’re locating a specific person (even if you don’t name them). Many speakers still prefer hay here.
- Very common in Spain when you hear a knock/bell: Llaman a la puerta or Han llamado a la puerta.
- For static location, Spanish uses en: alguien está en la puerta.
- A la puerta appears with action verbs: llamar a la puerta, asomarse a la puerta, salir a la puerta.
- With estar and haber (hay), the standard choice is en. You may hear Hay alguien a la puerta in some varieties, but en is the safest, most general option.