The most common reason: too many devices on one connection
If you measured your speed and got less than what your provider promised, the first place to look is how many things are using your internet right now. Every device connected to your wifi — phones, tablets, computers, smart TVs, security cameras, smart speakers — shares the same bandwidth. When several devices stream video, read files, or run updates at the same time, they compete for that shared pipe, and each one gets slower.
This is especially true if someone in your house is streaming 4K video or downloading a large file while you are trying to work. A single 4K stream can use 15 to 25 megabits per second on its own. If your plan is 100 megabits total and three people are streaming at once, you are splitting what is left among everyone else.
The fix is straightforward: turn off devices you are not using, or ask whoever is streaming to pause while you run your speed test. If slowness happens every evening around the same time, multiple devices are probably the culprit.
Key Takeaways
- Multiple devices streaming or downloading at the same time will slow your entire connection because they share one bandwidth pipe.
- Your router's location, age, and distance from your devices matter more than most people realize — a router in a closet or corner will deliver slower speeds than one in a central, open spot.
- Interference from other wifi networks, microwaves, and cordless phones can degrade your signal, especially on the 2.4 GHz band that older devices use.
- Your internet service provider may intentionally slow certain types of traffic, or your plan may have a data cap that triggers throttling once you hit a threshold.
- Wired connections (ethernet cable) will always be faster and more stable than wifi, so test with a cable if you suspect a wifi problem.
Your router is too far away or in a bad spot
Wifi signal weakens the farther you are from your router, and walls, metal, and dense materials block it. If your router sits in a bedroom closet or behind a filing cabinet, devices in other rooms will get a weaker signal and slower speeds. Even if your plan is fast, a weak signal means your device cannot use the full speed available.
The best location for a router is central, elevated, and away from obstacles. A shelf in a hallway or living room works better than a corner, a closet, or behind furniture. If you cannot move the router, the next best option is a wired connection — plug an ethernet cable directly from the router into your computer. Ethernet is not affected by distance or walls and will show you whether the problem is your wifi or your internet connection itself.
Your router is old or overheating
Routers have a lifespan. Most work well for three to five years, then start to degrade. An older router may not support the newer, faster wifi standards that newer devices expect. It may also have less memory and processing power, so it cannot handle as many devices at once.
Overheating also slows routers down. If your router is in a hot room, in direct sunlight, or stacked under other equipment, it may throttle itself to cool down. Check whether the router feels hot to the touch. If it does, move it to a cooler, more open spot and make sure air can flow around it.
If your router is more than five years old and you have already tried moving it and reducing the number of connected devices, replacing it may be the most practical fix. Newer routers are faster and handle more devices without slowing down.
Interference from other wifi networks and devices
Wifi uses radio frequencies, and those frequencies can get crowded. If you live in an apartment building or a dense neighborhood, dozens of other routers are broadcasting on the same channels as yours. This interference does not break your connection, but it degrades the signal quality and slows your speed.
Other devices also cause interference. Microwaves, cordless phones, baby monitors, and some wireless headphones broadcast on the 2.4 GHz frequency band, the same one older wifi devices use. If you have a microwave running while someone is using an older laptop on wifi, that laptop will slow down.
Modern routers broadcast on two bands: 2.4 GHz (slower, longer range, more interference) and 5 GHz (faster, shorter range, less interference). If your router supports both, newer devices should connect to the 5 GHz band. Check your router settings or ask your provider how to switch devices to the less crowded band. You can also change your wifi channel in the router settings — your provider or router manual will show you how.
Your internet service provider is throttling your speed
Some providers intentionally slow certain types of traffic. This is called throttling. They might slow video streaming, file sharing, or other bandwidth-heavy activities to manage network congestion during peak hours. This is legal in most places, though some states have rules about when and how providers can do it.
Throttling is different from a data cap. Some plans include a monthly data limit — say, 1 terabyte per month. Once you exceed that limit, the provider slows your entire connection until the next billing cycle. Check your bill or your provider's website to see whether your plan has a data cap and how much you have used this month.
If you suspect throttling, run your speed test at different times of day. If speeds are normal at midnight but slow at 7 p.m., throttling during peak hours is likely. If speeds drop suddenly after you hit a certain amount of data, a data cap is the cause. Contact your provider to confirm, or ask whether a higher-tier plan without a cap is available.
Background apps and updates are running without you knowing
Your devices may be downloading updates, backing up files to the cloud, or syncing data in the background while you are trying to use the internet. Windows and Mac computers often read system updates automatically. Phones back up photos and messages. Streaming apps cache content. All of this happens without a notification, and it uses your bandwidth.
Check what is running on your computer. On Windows, open Task Manager (press Ctrl+Shift+Esc) and look at the Network column to see which programs are using your connection. On Mac, open Activity Monitor (search for it in Spotlight), click the Network tab, and sort by Sent Bytes. If you see a large number next to an app you are not actively using, that app is the problem.
You can pause updates, disable cloud backups, or close apps that are not needed. Just be aware that some updates are important for security, so do not disable them permanently — instead, schedule them for a time when you do not need fast internet.
Your device itself is the bottleneck
Sometimes the problem is not your internet connection but the device you are testing on. An old computer with a slow wifi chip, or a phone far from the router, will show slow speeds even if your connection is fast. The device cannot receive the full speed available.
The clearest way to test this is with a wired connection. If you plug a computer directly into your router with an ethernet cable and run a speed test, you will see the true speed of your connection. If that speed matches what your provider promised, your wifi or your device is the problem. If the wired speed is also slow, your internet connection itself is the issue.
You can also test from different devices. If one phone shows slow speeds but another phone in the same room shows fast speeds, the first phone is the problem — it may need to be closer to the router, or its wifi chip may be failing.
Frequently Asked Questions
How do I know if my provider is throttling me?
Run speed tests at different times of day and compare the results. If speeds are consistently slower during evenings or weekends, throttling during peak hours is likely. If speeds drop suddenly after you use a certain amount of data, check your bill for a data cap. You can also contact your provider and ask directly whether throttling is happening on your account.
Will restarting my router actually help?
Yes, often. Routers can get stuck in a slow state or run out of memory after days of continuous use. Unplugging the router for 30 seconds and plugging it back in clears its memory and resets its connection to your provider. This is a quick first step before trying anything else.
Is wifi always slower than a wired connection?
Yes. Wifi is convenient but inherently slower and less stable than an ethernet cable. If you need the fastest possible speed for gaming, video calls, or large file transfers, plug in a cable. Wifi is fine for everyday browsing and streaming, but a wired connection will always be faster.
What speed should I actually expect?
Check your bill or your provider's website for your plan speed. That is the speed you should see when you run a test on a wired connection with no other devices using the internet. Wifi will be somewhat slower, and shared devices will reduce it further. If your wired speed is significantly lower than your plan speed, contact your provider.
Can I fix slow internet by changing my password?
Changing your wifi password will not make your internet faster, but it can prevent unauthorized devices from connecting and using your bandwidth. If you have never changed your password since you got the router, someone nearby may have connected without permission. Change it to a strong password and use WPA3 encryption if your router supports it.