The 25-country final of this year's 70th edition is being held on Saturday at the Wiener Stadthalle in the Austrian capital Vienna.Here is a look at how the competition is put together and how the all-important voting system works:HostsWinners host the following year's competition. Austrian vocalist Johannes Pietsch, known as JJ, triumphed at Basel in 2025 with his operatic song "Wasted Love".Who is taking part, and who is boycotting?The competition is organised by the European Broadcasting Union (EBU), the world's biggest public service media broadcasting alliance.Competing acts are selected by EBU member broadcasters representing their countries. This year, 35 countries entered.Spain, the Netherlands, Ireland, Iceland and Slovenia have pulled out in protest at Israel's participation, over the war in Gaza. It is the contest's biggest-ever political boycott.However, Bulgaria, Moldova and Romania have returned to the competition.After a random draw, the participating countries competed in two semi‑finals held earlier this week. Ten countries out of 15 qualified from each.Major financial backers Britain, France, Germany and Italy have reserved slots in the final, alongside the hosts, Austria, making up the 25 finalists.The songsThe song and artist can be chosen through televised national selection shows, an internal process or a mixed method.The songs have to be original and must not exceed three minutes.Lead vocals must be live, performed to a pre-recorded backing track.All performers must be at least 16 years old and a maximum of six performers may appear live on stage at the same time.Since 1999 the songs can be in any language. The lyrics and performances must avoid political, commercial or offensive content.Voting systemAll 35 participating countries get to vote in the final.Two sets of points, with equal weight, come from each country.