Fine in the morning, still good in the afternoon, then from eight in the evening everything slows. By the next morning it is normal again.
A pattern like this is actually good news: it narrows the possible causes dramatically. Hardware faults do not keep to a schedule.
Record the pattern first
Before changing anything, gather data over three days. Run a speed test over a LAN cable at four times: morning, midday, late afternoon, and evening. How to do it is in the guide to checking internet speed.
The shape of the pattern points straight at the cause:
| Pattern observed | Most likely cause |
|---|---|
| Slow only between 7 and 11 pm | Peak-hour congestion |
| Slow all day, starting on a particular date | Fair-use cap exceeded |
| Slow whenever people are home | Devices in your own house |
| Slow at irregular times | A fault, worth reporting |
| Slow in one app only | That service's servers, not your connection |
Peak-hour congestion
Providers do not provision full capacity for every customer simultaneously. Capacity is shared on the assumption that not everyone uses it at once, and that assumption holds for twenty hours a day.
Eight to eleven in the evening is when the assumption is under most strain. A drop to around half speed still counts as normal in many areas.
What you can do is limited, but not nothing:
- Schedule large downloads outside peak hours. System updates and automatic backups often run at exactly the worst time.
- Move to 5 GHz where devices support it. This adds no capacity from the provider, but removes congestion inside the house, and the neighbours crowd 2.4 GHz at the same hours too.
- Check the channel. In the evening, the number of active neighbouring networks rises. How to check is in the guide to Wi-Fi signal analyser apps.
Before blaming the provider. Congestion inside the house often peaks at the same hour as congestion outside it. Evening is when everyone comes home, switches on the television, and picks up their phone. Test by switching Wi-Fi off on every device but one, then measuring again.
The fair use cap
Many home packages include a monthly quota. Once exceeded, speed is reduced until the next billing period.
Its signature is clear and easy to distinguish: the reduction ignores the clock, starts on a particular date, and lifts on its own when the month rolls over.
If that is the pattern you have, check the subscription terms or the customer app to find the threshold. Some providers show remaining quota; some do not mention it at all unless asked.
When the cause is inside the house
There is a third pattern often mistaken for peak hours: slowness that follows people being home, not the clock.
Test it this way, at the hour that usually causes trouble, switch Wi-Fi off on every device but one, then measure. If it improves immediately, your capacity is genuinely being divided among too many devices inside the house, and the provider has nothing to do with it.
Two steps that help: cap speed per device through the QoS menu, and find whichever device is downloading in the background. Games consoles and computers updating their systems are the most frequent suspects.
If you suspect an unfamiliar device is piggybacking, how to confirm it is in the guide to spotting a compromised Wi-Fi network.
When it genuinely is worth reporting
Four situations worth raising:
- Speed over cable consistently below the promised minimum percentage, even outside peak hours.
- A drop far deeper than reasonable, down to a tenth, say.
- Irregular slowness following no pattern at all, particularly alongside disconnections, see the guide to Wi-Fi that keeps disconnecting.
- A situation that has deteriorated after months of being fine.
Bring the pattern you have recorded. A complaint carrying three days of data at different hours is handled very differently from "my internet is slow". Your rights as a customer and the escalation route are covered in the guide to customer rights when the internet is slow.
Frequently asked questions
Why is the internet always slow in the evening?
Because network capacity in your area is shared with neighbours, and eight to eleven at night is when everyone's usage peaks. Up to a point this is normal behaviour, not a fault.
What is a fair use policy and how do you find yours?
It is a reasonable-use cap. Once a certain quota is exceeded within a month, speed is reduced until the next period. The figure appears in the subscription terms, and some providers show it in their customer app.
How do you tell a fair-use cap from peak-hour congestion?
A fair-use cap applies all day and does not lift until the month rolls over. Peak-hour congestion appears only at certain hours and disappears outside them. If it also feels slow at ten in the morning, suspect the cap.
Does changing DNS help at peak hours?
A little, and only for the part that looks up site addresses. If what is congested is the capacity of the link itself, DNS changes nothing. A noticeable improvement after changing DNS usually means the problem really was DNS, not capacity.
