What affects broadband speed?

Post Office Broadband Connect

This article will help you understand what affects your broadband speeds which can help solve or at least pinpoint the cause of any broadband speed problems.

Please also read our support article Fix slow broadband speed for more specific advice on how to fix common broadband speed related issues.

Setting up your wireless router incorrectly or using wrong equipment can cause slow broadband speeds. Here are some common mistakes to try avoid.

  • Your master socket: Always make sure your wireless router is plugged into your Master phone socket rather than extension sockets. (Extension sockets connect to your master socket using wiring that isn't built for sending broadband signals so you won’t get the best possible speeds)


Your master phone socket can usually be found in your hallway or near your front door and will be bigger than any other socket in your house.

  • Micro-filters: Make sure your micro filters are installed properly – these filter your phone line and let your broadband and phone work at the same time. If you don't use them, your Wi-Fi connection may start dropping or feel slow.


If your master phone socket has 2 ports (see below) this means it’s a pre-filtered master socket so your line is already split between your phone and broadband connection. You can just plug your phone and wireless router straight into this socket without using any micro-filters.

  • Extension cables: If your wireless router is far away from your master socket and connected by an extension cable, make sure you aren’t using a standard telephone cable. These aren’t designed to carry broadband signals and will likely cause slow speeds. We recommend using getting a longer Ethernet cable or using an ADSL extension cable instead.
  • Your home wiring: Its age, length and condition all affect broadband speed. You’ll probably get faster speeds if the wiring from your master socket to the router is shorter and of good quality.


  • Furniture and appliances: Doors, wardrobes and other electrical devices like baby monitors, cordless phones, microwaves and washing machines can interfere with the signal.


  • Sharing your connection: Your broadband speed is split between every device that’s connected to your wireless router. If mum’s on her mobile, dad’s using his laptop and the kids are streaming movies and gaming on different devices, the signal is split between them and the broadband speed might slow down. Try switching off any wireless devices you’re not using to improve speeds.


  • Your building: Wi-Fi can pass through most obstacles easily, however, materials like brick, plaster, cement, stone, metal and double-glazed glass can block some of the signals. Some newer homes may even have plasterboard walls that are backed with aluminium foil, which can act as a barrier to Wi-Fi.


  • House size: The larger your house, the less likely it is that you’ll get a strong Wi-Fi signal in every room. We recommend using a Wi-Fi Extenders or Wi-Fi mesh systems to boost broadband signals in rooms that may have Wi-Fi weak spots. These are available from most electronic retailers.
  • How close you live to the phone exchange: Broadband signal has to travel from your local phone exchange to your line. The shorter the distance, the faster the connection.


  • Network damage: Heavy rain, flooding and snow can all cause short circuits and cable damage, which can slow or stop your broadband connection. Cable damage can cause problems with your phone and broadband connection, such as slow speeds, a crackly phone line or no dial tone.


  • Peak times: Lots of people are usually online at the same time between 6pm and 9pm and on weekends – your broadband may be slower at these times because of the congestion on the network. If a lot of people are using a website at the same time, you might find it takes longer to load. Unfortunately there’s not much we can do about this except recommend that you try again later.
  • Using slower, older computers and devices: Generally, smaller, older and lower-quality devices will deliver slower broadband speeds than newer laptops and desktop computers.


  • Wired connection: A wired connection will always be faster and more stable than a wireless connection. If you want faster speeds, try connecting to your router with an Ethernet cable.


  • Software and applications: Running lots of different applications sometimes gives the impression that your broadband is running slow but this could just be down to the age and condition of your device and running large applications.


  • Viruses and spyware: Virus and Spyware can slows your device down, leaving little computing power for much else. Installing good security software on all your devices can help protect you against attacks. All Post Office Broadband customers can take advantage of the 6 months free internet security offer from F-Secure worth £39.99.

Existing customers

Broadband and HomePhone Support

8am to 8pm, Monday to Saturday

9am to 6pm, Sunday

0345 600 3210

0345 600 3210