The internal working language of the ECB is generally English, and press conferences are usually held in English. External communications are handled flexibly: English is preferred (though not exclusively) for communication within the ESCB (i.e. with other central banks) and with financial markets; communication with other national bodies and with EU citizens is normally in their respective language, but the ECB website is predominantly English; official documents such as the Annual Report are in the official languages of the EU.
How are the languages of official documents handled?
the official languages of the EU