The design of one is predominantly blue, the other red. But the features of social-networking sites Facebook and StudiVZ are so similar that Facebook believes its rival has copied its features and software.
Facebook says its German rival's look and content are too close for comfort
The German offshoot of the social-networking website Facebook has started legal action against rival website StudiVZ after claiming that StudiVZ has illegally copied Facebook's software code.
In an opening court hearing in Cologne on Tuesday, Facebook claimed that StudiVZ's logo and features infringed on Facebook's intellectual property rights and that StudiVZ must have obtained illegal access to Facebook's source code.
A screengrab shows the design and layout of StudiVZ
Independent opinion needed?
One Cologne judge suggested the dispute should be put in the hands of an independent evaluator to establish whether any souce code has been copied.
To do this, an evaluator would compare source codes of both parties, to see what, if anything, was copied. If there is agreement, the court would then reach a decision by mid June.
StudiVZ is Germany's market leading social-networking site with around 5.5 million registered users. The website was founded in 2005 and taken over in 2007 by the Holtzbrink publishing concern in a deal valued at more than 50 million euros ($66 million).
Facebook, launched in 2004, has more than 200 million world-wide users; 2 million of them are in Germany.