Gratuito vs. gratis

The Spanish words 'gratuito' and 'gratis' share a similar meaning referring to that which costs nothing or is free. However, their usage differs slightly depending on the context in which they are used.

Gratuito

'Gratuito' is often used to describe services, things, or actions that are provided without any charge or payment. It is typically used in formal contexts or when referring to more significant items or services that are being offered at no cost.
El servicio de salud es gratuito en este país.
(The health service is free in this country.)
Los museos ofrecen entrada gratuita los domingos.
(Museums offer free admission on Sundays.)
Proporcionamos capacitación gratuita a nuestros empleados.
(We provide free training to our employees.)

Gratis

'Gratis' is a bit more informal and it's often used to denote minor items or additional bonuses that come with no cost. The term is commonly seen in advertising for promotional offers.
Compra uno y llévate otro gratis.
(Buy one and get one free.)
Descarga esta aplicación, es gratis.
(Download this app, it's free.)
Te regalan una copa gratis con tu entrada.
(You get a free drink with your ticket.)

Summary

'Gratuito' and 'gratis' both refer to something being free or not costing anything in Spanish. However, they are used differently depending on the formality of the situation and what's being described as free. 'Gratuito' usually refers to larger, more substantial things or services that are provided free of charge and is used in a more formal context. Meanwhile, 'gratis' often refers to smaller items or additional benefits and is usually seen in advertising.