Facebook, Google, Yahoo and other sites involved in trial amid fears some web users will not be able to access new addresses
There are concerns that some web users' routers may not work with IPv6 addresses and they will have to buy new devices such as this one from AVM. Photograph: AVM/EPA
Facebook, Google, Yahoo and hundreds of the world's largest websites are now testing the enormously expanded internet address system, known as IPv6, in preparation for the time – expected within the next year – when it becomes impossible to add new sites to the web using the existing system, called IPv4.
The biggest problem though in implementing the new system lies inside people's homes – where barely any of the broadband routers now in use can handle the new system.
In the UK, the communications minister Ed Vaizey is marking World IPv6 Day with an industry summit to discuss progress on switching to the new protocol. Vaizey said: "We must ensure we create the conditions that allow the internet to continue to grow and for companies to produce fresh innovations. IPv6 is key to the continued growth of the internet. It is essential industry deals with the switchover before there is an impact on the internet."