Who is blamed for starting ww1?

Germany was officially found solely responsible for WWI according to the Treaty of Versailles.

However, there are a serious of events that led to WWI. Who caused it is open to interpretation.

Archduke Francis Ferdinand, in line to the throne of Austia-Hungary, was assassinated by a Serbian nationalist while he was in the Balkans. The Balkans, including Serbia, were controlled by Austria-Hungary, and angered them. They gave Serbia an ultimatum with numerous demands. Serbia agreed, but Austria-Hungary declared war anyway. Since Austria-Hungary was in an alliance with Germany and Italy, they also indirectly declared war as well.

Russia, who was like Serbia's big brother, got upset and mobilized their troops on their border, waiting to come to Serbia's aide. However, Russia shared a border with Germany. Germany felt threatened by this and declared war on Russia. But Russia too was also in an alliance with France and Great Britain. While all of these countries had colonies all over the world, thus how it became a world war.

A reason for why the Allied Powers found Germany responsible is because they made the first battle move..... By surprise-attacking France. They went through a neutral country, Belgium, to do it; murdering and killing innocent Belgians in the process.

Austria-Hungary was the first to officially declare war, though it was on a country that wasn't in an alliance. Germany was the first to declare war on a country that was in an alliance.

It's open to interpretation on who started the war.