Christmas tree lights can slow your wi-fi warns watchdog Ofcom as it releases an app that can check home broadband. The app samples wireless signals to see if data is flowing uninterrupted from routers to phones and tablets. The app is released alongside research which suggests wi-fi in six million homes and offices is not running as fast as it could do. The app also provides tips to help people spot what might be slowing down their wi-fi speed. Interference could come from other electronic devices such as baby monitors, microwaves or Christmas fairy lights, said Ofcom. Fairy lights could 'slow' wi-fi speeds warns Ofcom - BBC News