The short answer: start by running a speed test over a wired ethernet connection directly to your router. If the wired speed matches what you are paying for, the problem is your Wi-Fi rather than your broadband line. If the wired speed is also well below what was advertised, you have a genuine broadband fault or contention issue worth investigating further.
Step one: work out whether it is Wi-Fi or broadband
Most slow broadband complaints turn out to be Wi-Fi problems. Before doing anything else, plug a laptop or computer directly into your router using an ethernet cable and run a speed test at Speedtest.net or the Ofcom broadband speed checker. Run the test two or three times at different points in the day and note the results.
If your wired speed is close to what you are paying for, your broadband line itself is fine. The problem lies between your router and your devices. Head straight to the Wi-Fi section below and our guide to improving your home Wi-Fi.
If your wired speed is consistently well below what you were quoted, the fault is likely on the line, at your exchange, or with your provider's network. Keep reading.
When running a speed test, close all other applications and make sure no other devices are downloading or streaming. Even a single device running a software update in the background can skew your results.
Wi-Fi signal issues
Wi-Fi is the most common culprit for perceived slow broadband. A few things affect it significantly.
Distance and physical obstructions
Wi-Fi signal weakens with distance and degrades further when it passes through walls, floors, and ceilings. Thick masonry walls, concrete floors, and metal structures are particularly disruptive. A router at one end of a house may deliver only a fraction of its full speed at the far end.
Move the router to a central position in your home, raised off the floor, away from walls where possible. This one change improves Wi-Fi coverage more reliably than most other fixes.
The 2.4 GHz band is congested
Most routers broadcast on two frequency bands: 2.4 GHz and 5 GHz. The 2.4 GHz band has a longer range but is shared with neighbouring Wi-Fi networks, microwaves, baby monitors, cordless phones, and Bluetooth devices. In flats and terraced streets, it is frequently crowded.
The 5 GHz band is faster and far less congested, but has a shorter range. For devices within reasonable distance of the router, connecting them to the 5 GHz band often produces a marked improvement. Check your router settings or app to make sure 5 GHz is enabled and that your devices are connecting to it rather than defaulting to 2.4 GHz.
Interference from other devices
Microwaves operating at 2.4 GHz can temporarily disrupt Wi-Fi for nearby devices. Baby monitors are a frequent offender. Cordless phones in the same frequency range can also cause intermittent slowdowns. If your broadband seems slow only at certain times and only on Wi-Fi, try identifying whether a nearby device is active at the same time.
For a more detailed breakdown of fixes, see our home Wi-Fi improvement guide.
Time of day and network congestion
If your broadband is fine in the morning but noticeably slower in the evenings, particularly between 7pm and 11pm, you are experiencing network congestion. This is an ISP-side issue, not a problem with your equipment.
Most broadband connections involve shared infrastructure at some point between your home and the wider internet. When many customers in the same area are using the connection simultaneously, the available bandwidth per household drops. Budget providers with less network capacity per customer tend to have worse peak-time congestion than premium ones.
Run your speed tests at different times: early morning, mid-afternoon, and around 8pm or 9pm. If there is a large gap between the morning and evening results on a wired connection, the issue is with your provider's network capacity in your area. Contact your provider and report it as a fault. If they cannot resolve it, you may have grounds to exit your contract early.
Old or faulty router
The router your ISP provides is often a basic model. An older router, particularly one that is five or more years old, may not support the Wi-Fi standards needed to take full advantage of faster connections, or may be struggling under the demands of a home with many connected devices.
Restarting your router is always worth trying first. Power it off completely, wait 30 seconds, and power it back on. This clears cached connections and can resolve temporary performance issues. If your router restarts itself regularly, that is a sign it may be developing a fault.
If you have had the same ISP-supplied router for several years and your speeds have gradually declined, ask your provider for a router replacement. Most will send one free of charge if you report a fault. Alternatively, purchasing a third-party router that supports modern Wi-Fi standards (Wi-Fi 5 or Wi-Fi 6) can produce meaningful improvements, particularly in larger homes or those with many devices.
Line quality and distance from the cabinet (FTTC connections)
If you are on a part-fibre (FTTC) connection, meaning fibre runs to a street cabinet and then copper runs from the cabinet to your home, your speed depends in part on the length and condition of that copper section.
Copper cable degrades the signal over distance. Properties more than 300 metres from the cabinet typically see noticeably lower speeds than properties right next to it. Properties very far from the cabinet, or on old or damaged copper, may receive significantly less than the advertised maximum.
You cannot change the physical distance, but switching to a full fibre (FTTP) connection if it is available in your area would remove the copper section entirely. Check your postcode to see whether full fibre providers cover your address. Read our broadband speeds explained guide for more on how FTTC and FTTP affect the speeds you actually receive.
Microfilters and the master socket (ADSL and FTTC)
On ADSL and FTTC connections, broadband and phone signals share the same copper line. Microfilters are small adaptors that separate the two signals and must be plugged into every active phone socket in the house. A missing, damaged, or incorrectly fitted microfilter can drag down your broadband speeds across the whole property.
Test from the master socket. This is the original BT socket installed in the property, usually near the front door or in the hallway. It has a slightly different face plate from extension sockets and may have a small horizontal line dividing it. Plug your router directly into the master socket, bypassing any extension cables or other sockets. If your speed improves, the problem is with the internal wiring or an extension socket rather than the external line.
If you do not know which socket is the master, try the one in the most prominent location near the point where the phone line enters the building. Contact your provider if you are unsure.
Too many devices using bandwidth simultaneously
Modern households have a large number of connected devices. Streaming 4K video on multiple screens, large game downloads running in the background, video calls, smart home devices, and cloud backups all consume bandwidth at the same time. On a 35 Mbps FTTC connection, the combined demand can easily approach the available capacity.
Check which devices are actively using the network. Most modern routers have a connected devices list in the admin interface, often accessible at 192.168.1.1 or via a smartphone app. Look for devices running unexpected background downloads. Gaming consoles and smart TVs are common culprits for large background updates that run without any visible indication.
If your household regularly has many devices in use simultaneously, upgrading to a faster connection tier may simply be the right answer.
Your provider's network quality
Not all broadband providers are equal in terms of network investment. Budget providers often run more contended networks, meaning more customers share the same capacity. This is how they keep prices low. During peak hours, customers on heavily contended networks experience more pronounced slowdowns than those on less contended premium networks.
Ofcom publishes annual research on residential broadband performance that includes comparisons between providers. If you are consistently experiencing slow speeds and your provider cannot resolve the issue, reading that research and considering a switch is worthwhile. Our broadband switching guide explains the process, including what happens to your existing contract when you move.
A genuine broadband fault on the line
If your speed is consistently poor at all times of day, even on a wired connection, and none of the above causes apply, you likely have a genuine fault. Signs include speeds that are well below your guaranteed minimum, connections that drop and reconnect frequently, or speeds that have declined suddenly after a period of being fine.
Contact your provider and report a fault. They will run line diagnostics remotely and, if needed, arrange for an engineer visit. Under Ofcom's rules, your provider must fix faults within a reasonable time. If the fault is not resolved within 30 days, you have the right to exit your contract early without paying an early termination fee.
Before calling, note down the following: when the problem started, whether it affects wired and Wi-Fi connections, the speed you are getting versus what you were quoted, and results from speed tests run at different times. This information will speed up the fault investigation.
Your guaranteed minimum speed
When you signed up for your broadband package, your provider was required by Ofcom to tell you a guaranteed minimum speed. This is a specific figure that appears in your contract or welcome documentation, not the advertised headline speed.
If your connection is consistently below that guaranteed minimum, contact your provider and quote it to them. They are obligated to fix the fault. If they fail to bring your speed above the guaranteed minimum within 30 days of you reporting the problem, you can exit the contract without penalty. Keep a record of your speed test results and the dates you reported the issue, as this supports your case.
Read our broadband speeds explained guide for more detail on how guaranteed minimum speeds work and how to find yours.
When to switch provider
If your speeds are consistently poor, you have ruled out Wi-Fi and equipment issues, you have reported a fault to your provider, and they have not resolved it within 30 days, switching is the sensible next step. Moving to a provider with better network capacity in your area, or upgrading from FTTC to full fibre if it is now available, can make a significant practical difference.
Switching broadband is straightforward in the UK. In most cases you do not need to contact your old provider first. The new provider handles the transfer. Our guide to switching broadband covers the full process, including what to check before signing up with a new provider.
What you do not need
- You do not need to buy a signal booster before checking the basics. Repositioning your router and switching to the 5 GHz band resolves most Wi-Fi issues without any additional hardware.
- You do not need to upgrade to gigabit broadband to fix slow speeds. The problem is usually with your existing setup or your provider's network, not your speed tier.
- You do not need a third-party engineer before reporting the fault to your provider. Your ISP is responsible for diagnosing and fixing line faults. They will arrange any necessary engineer visit at no cost to you if the fault is on their side of the network.
- You do not need to reset your router to factory settings. A simple restart (power off and on) is usually sufficient. A factory reset removes your Wi-Fi settings and any custom configuration, which creates extra work without usually fixing the underlying problem.
- You do not need to accept a slow connection. You have consumer rights under Ofcom's rules. If your speed falls below the guaranteed minimum and your provider cannot fix it, you are entitled to exit your contract early.
Frequently asked questions
How do I run a proper broadband speed test?
Connect your computer or laptop to the router using an ethernet cable. Close all other applications. Make sure no other devices are streaming or downloading. Go to Speedtest.net or the Ofcom broadband speed checker and run the test. Record the download speed, upload speed, and ping. Repeat this at different times of day, including early morning and around 8pm to 9pm, so you have a picture of how performance varies. The results on a wired connection are your true broadband speed, separate from any Wi-Fi issues.
My broadband is only slow in the evenings. What is causing it?
This is almost certainly peak-time network congestion. When many customers in your area are using the internet simultaneously, the shared capacity at your provider's local infrastructure gets stretched. Budget providers tend to have less spare capacity and show worse peak-time performance. Run a wired speed test at 8am and again at 8pm on the same day. If there is a large gap between the two results, report it to your provider as a fault. If they cannot resolve it, this may give you grounds to exit your contract early.
My broadband was fine and has suddenly got much slower. What happened?
A sudden drop in speed usually points to a line fault, a change in the network near your exchange, or a faulty router. Start by restarting the router. If that does not help, run a wired speed test to rule out Wi-Fi. If the wired speed has dropped, contact your provider and report it as a fault, noting the date the problem started and what speed you are now getting versus before. Sudden degradation is a clear sign of a fault rather than a gradual infrastructure issue.
Can my neighbours' Wi-Fi slow down my broadband?
Neighbouring Wi-Fi networks do not slow down your actual broadband line, but they can interfere with your Wi-Fi signal if they are using the same channel on the 2.4 GHz band. This makes your Wi-Fi connection to your router slower, which feels like slow broadband. Switching to the 5 GHz band largely avoids this problem as it has more available channels and is less commonly used by neighbouring networks. Your router may have an automatic channel selection option that helps reduce interference on 2.4 GHz as well.
What is the guaranteed minimum speed and how do I find mine?
The guaranteed minimum speed is a specific speed your provider committed to delivering when you signed up. It is lower than the advertised headline speed and represents the lowest performance you should consistently receive. It should appear in your contract documents or welcome email. If you cannot find it, call your provider and ask them to confirm it. If your measured speeds on a wired connection are consistently below this figure, your provider is obligated to fix the fault or release you from the contract.
Will switching to full fibre fix my slow broadband?
If you are currently on an FTTC (part-fibre) connection and your speed is limited by a long copper run from the street cabinet, upgrading to full fibre (FTTP) would remove that bottleneck entirely. Full fibre delivers speeds over a fibre cable all the way to your home rather than relying on copper for the final section. If full fibre is available at your address and you are experiencing consistent underperformance on FTTC, switching is likely to produce a meaningful improvement. Check your postcode to see which full fibre providers cover your area.
My speed test shows good results but streaming still buffers. Why?
A good headline download speed does not always mean the connection is performing well for streaming. Factors that cause buffering despite adequate download speeds include high latency (ping), packet loss on the connection, or the specific streaming service's servers being congested at that moment. Run your speed test and note the ping figure as well as the download speed. A ping consistently above 50ms on a fixed-line connection, or any packet loss, suggests a line quality issue worth reporting. You can also check whether the buffering happens on all services or just one particular platform, as the latter points to that service rather than your broadband.
Can I exit my broadband contract early because of slow speeds?
Yes, in certain circumstances. Under Ofcom's rules, if your speeds fall below the guaranteed minimum speed set out in your contract and your provider fails to fix the problem within 30 days of you reporting it, you have the right to exit the contract without paying an early termination fee. You must formally report the fault to your provider first and give them the 30-day window to resolve it. Keep records of your speed tests and the dates you raised the complaint. Our switching guide explains what to do once you have decided to move to a different provider.