Christmas fairy lights could cause slower broadband speeds, regulator Ofcom has warned.
The warning came as it released an app to check home broadband networks for interrupted signals between wireless routers and devices like phones and tablets.
Ofcom says that up to six millions homes and offices could improve their broadband connection.
It said networks are often not set-up correctly, and can suffer interference from electronics ranging from baby monitors to fairy lights.
This is because electronic devices which emit radio waves can affect Wi-Fi transmission.
People are advised to keep their router as far away as possible from other electronic devices.
The free Wi-Fi Checker app allows people to test the quality of their internet signal and suggests ways to enhance it.
New Ofcom research says around a quarter of UK homes have "superfast" broadband connections of more than 30MB per second, an increase of 1.5 million homes.
However in rural areas fewer than two-fifths of homes have access to the higher-speed connection.
Some 8% of households cannot receive a connection with speeds of more than 10MB per second, the report adds.
Ofcom says that in rural areas this is due to remote houses "lying further from the network’s local street cabinet or local telephone exchange".
It said that small businesses in particular are struggling with slow connections.
It says that almost half are unable to get more than 10MB per second, and says that by 2017 around 20% will be unable to access superfast connections.
Ofcom says 10MB per second is the "tipping point" at which customers rate their broadband as good.
Ultrafast broadband – with speeds of more than 300MB per second – is available to half a million homes in the UK.
Mobile 4G coverage has also increased across the major networks, from 44% in 2014 to 73% this year.
Ofcom chief executive Sharon White said: "Mobile and broadband have become the fourth essential service, alongside gas, electricity and water.
"There's been a technological revolution over recent years, with 4G mobile and superfast continuing to extend across the country."