Por vs para: a practical guide
Both por and para often land on the English word “for”, which is exactly why they blur together. The clean way to keep them apart: para points forward to a goal or destination, while por points to a cause, a means, or movement through something.
Para = goal, destination, deadline
Use para when there is a target ahead: purpose (estudio para aprender, I study in order to learn), recipient (es para ti, it is for you), destination (salgo para Madrid, I leave for Madrid), and deadlines (para el lunes, by Monday). If you can rephrase with “in order to” or “destined for”, it is para.
Por = cause, exchange, duration, route
Use por for the reasons and means behind something: cause (lo hago por amor, I do it out of love), exchange (gracias por todo; lo compré por 10 euros), duration (por dos horas), and movement through (caminamos por el parque, we walked through the park). “Because of”, “in exchange for”, “through” all signal por.
The contrast in one pair
Put them side by side and the logic shows: lo hago por ti = I do it because of you / for your sake (you are the motive), whereas lo hago para ti = I do it for you (you are the recipient/goal). Same English “for you”, but two different relationships: motive vs destination.
Fixed expressions worth memorising
Some phrases just lock to one preposition and are best learned whole: por favor, por supuesto, por ejemplo, por fin, por eso; para siempre, para nada, estar para. Treating these as vocabulary rather than grammar saves you from re-deriving the rule mid-sentence.
Build intuition through repetition
Por/para is a decision you make constantly in speech, so it has to be fast, not reasoned. That only comes from volume. Meeting the two in contrasting example sentences, the way Verboteca schedules them, turns the choice from a calculation into a reflex.