A sworn translation is a translation that is carried out by a sworn translator accredited by the Spanish Ministry of Foreign Affairs. The sworn translator acts as a Notary Public, attesting to the accuracy of the translated document.
This type of translation is required by certain authorities (Ministry, Court, Academic Institutions). It is these bodies, whether Spanish or foreign, that require that the translation to be presented be sworn.
On the other hand, a sworn translation can be used to guarantee the translated information, given that the translator assumes responsibility for the translation with their recognised signature and stamp.
The Hague Apostille is one way of validating the authenticity of a public document or its extension. Not all countries belong to this Convention, though the Ministry of Justice provides a very detailed explanation of everything concerning this procedure, here: https://www.mjusticia.gob.es/es/ciudadania/tramites/legalizacion-unica-apostilla
How does The Hague Apostille impact the sworn translation? Quite a lot: this Apostille must be included in the translation, as otherwise, the translation will not be deemed valid.
Depending on the document, the country, the body requesting it, etc., there are a number of methods to legalise documents. Although the most common is The Hague Apostille, not all countries belong to this Convention. All the information concerning the legalisation of documents can be found at the Ministry of Foreign Affairs, European Union and Cooperation: https://www.exteriores.gob.es/es/ServiciosAlCiudadano/Paginas/Legalizacion-y-apostilla.aspx
Not all countries have the same sworn translation procedures; therefore, it is essential to ensure that the sworn translators accredited in Spain, who are to attest to the translation, are accepted by the requesting body, especially if it is not Spanish.
The United Kingdom, for instance, does not have sworn translators per se, as they are governed by Common Law, but rather, translations are certified by qualified translators belonging to the ITI (Institute of Translation and Interpreting).
While it is true that, prior to COVID-19, sworn translations were always required to be presented in hard copy, the administration has since had to modernise.
As a result, as of 2020, a growing number of bodies have been following suit—sworn translators who have their digital certificates installed can use their electronic signature on their translations without having to scan them and send them in hard copy, thus saving time and costs for the client, as well as the need for sworn copies, as an electronically signed translation can be reused for several procedures.
However, some institutions remain reluctant towards electronic signatures and thus continue to require a hard copy format—be mindful of this!