Yes, if it isn't in English or Irish. ISD asks for a full translation that includes the translator's confirmation that it is accurate, the date, the translator's full name and signature, and their contact details. Every VisaDocTranslation translation includes all four.
The word ISD uses is 'full', and it means it. The translation covers the registration number, the registrar's notes, the annotations added years later and the stamp in the corner that nobody has been able to read since the day it was pressed. A summary of 'the important bits' is exactly the kind of thing that gets an application parked while ISD writes back for more.
If the certificate was issued in an EU country, ask the issuing office for a Multilingual Standard Form (MSF). ISD says that where an MSF comes with an EU-issued birth, marriage, death or divorce certificate, no translation is needed. For everything else, upload the whole certificate, front and back, and we translate every page.