Why is my internet connection slow?

We know that slow internet interrupts life. Slow internet speed can be caused by a range of factors, which makes it a challenge to pinpoint the exact cause. However, there are some things you can do to get the best speed possible from your service before calling for repair.


  1. Check your modem/router
  2. Consider bandwidth and usage
  3. Optimize WiFi setup
  4. Adjust device settings
  5. Check your wiring


Think you might have an internet outage? If your service appears to be down completely, get help on our outage page. This page only addresses a slow or spotty internet connection.

Pro tip: It can be useful to run a speed test before troubleshooting for a slow internet connection. Then, after following the steps here, run the test again to see the improvement for yourself.

1. Check your modem/router

Your connection speed depends a lot on how your modem/router is running. (Note: Since your CenturyLink equipment is a combination modem and router, we use both words in this article.) 

Adjust your router position


You might be surprised by how much your internet speed can be impacted by where your router sits. You want to find a spot that is up off the floor and centrally located in your home (or in the area of your home where most internet activity takes place).

Physical obstructions can also be major culprits in slowing down your WiFi speed. Look out for any of these things standing between your router and your connected devices:


  • Brick or concrete walls or floors
  • Thick, heavy doors or windows
  • Large containers of water (such as fish tanks) 
  • Large metal appliances (especially refrigerators) 


Do your best to move the router or move other items so that these things are not blocking the path between your router and your devices.


Reboot your router


Routers can get bogged down after running for a while. The easiest way to fix many connectivity problems is to restart your router. If you find you're needing to restart frequently, it's easier than ever to set up a daily or weekly reboot to keep things running smoothly.

Check for firmware updates


Next, check to see if you need to update your modem's firmware. This is key to making sure this essential piece of equipment is free of bugs and running optimally.

As a last resort, you can try resetting your modem. Similar to resetting a smartphone or reinstalling a computer's operating system, this will erase custom settings and return the modem to its factory default status.

Customers with Fiber Internet service have specific equipment requirements. With a connection that fast, you need to make sure your gateway (modem) can keep up. If your service is connected using a different modem, you may not be getting top performance from your service.

2. Bandwidth needs and usage

How many devices are using up your bandwidth?

Start by understanding internet and WiFi speeds, and how they relate to all the connected devices in your home. The combined bandwidth used by all your devices may be more than you think. And the more bandwidth is used, the less speed you see on any one device. Use a bandwidth table to calculate your household's peak hour usage. Don't forget to include all of the following connected devices (and there very well may be more):  


  • Smartphones, computers and tablets
  • Web-enabled cameras or smart home security systems 
  • DVRs, smart TVs,  and video streaming devices
  • Additional routers, VoIP phones, wireless printers
  • Voice assistants and smart speakers (like Alexa and Google Home)


Many of these devices are always on and frequently run updates or backups in the background, all of which can slow internet speeds down quite a bit. Whenever possible, power off or disconnect devices that you aren't using. This can free up more speed for the ones you are using. You may also want to check device settings to ensure backups aren't scheduled at the same time as your personal use peak hours. 


The key is, needs vary widely. One person living alone could easily get by with a 5 Mbps connection, while a large household doing multiple activities may need at least 20 Mbps. Set realistic expectations — depending on your plan speed, you may not be able to have three family members videoconferencing, streaming TV, and gaming online at the same time. Those three activities in particular require substantial upload speeds as well as download, so check your plan.

Special notes related to speed

Peak hours: When the majority of households are online, internet traffic slows down across all networks. This is usually from about 7 p.m. to 11 p.m. You may notice that your internet is slower at these times.


Consider the role of various web hosts: Content providers and apps send out huge volumes of high-bandwidth video content worldwide. If a video streaming provider is getting more demand than their bandwidth can handle, this can cause video buffering — meaning it lags or sticks while loading. 

3. Optimize your WiFi setup

What we think of as "slow internet" can sometimes be a weak WiFi signal. Wireless speeds tend to be less than wired speeds on the same network, due to interference and signal loss over distance. But there are ways you can make sure your WiFi is running as fast as possible. 


Optimize your router. See #1 above.


Reduce interference from other electronics. Other devices in your home can slow down your WiFi connection, including microwaves, cordless phones, Bluetooth devices, TVs, wireless security systems, baby monitors, garage door openers, and more. If you have a newer modem, opt for a 5 GHz frequency signal to get a stronger connection and avoid some congestion from surrounding devices, many of which use the 2.4 GHz band.

Electronic interference graphic

Protect your WiFi network with a good password. If you don’t have a strong password, anyone close to your home can access your WiFi network and cause it to slow down. There are other ways you can ensure a secure network as well.

Consider a WiFi extender. If your service is weak in parts of your home that are farther away from your router, a WiFi extender can increase your signal coverage in more distant areas.

4. Check your device settings

Your base connection and your WiFi are only part of the speed equation — all the devices that you connect to your internet also play a role. To get the best performance, make sure devices, apps and software are up to date, free of malware, and not being overloaded.


Run antivirus scans on all devices


Antivirus protection is essential for good performance. Viruses and malware can slow down your whole system, including internet speed performance. Make sure every device is healthy by installing well-rated security software, keeping it updated and running security scans at least weekly. CenturyLink internet subscribers can get McAfee protection for free on two devices.


Update your browser


Your web browser (Chrome, Edge, Safari, Firefox, etc.) plays a major role in your experience when you are online. Make sure yours is running smoothly.

  • Update your browser. Make sure your browser software and all plug-ins and extensions (like Java, Silverlight and others) are up to date. You can use a third-party website to do a browser check, and visit the support site for each browser to download any needed updates or get additional help.

  • Clear cache on a regular basis. Your browser saves data from most websites you visit, which over time can slow everything down. Look in your browser settings and tools for "Clear cache, cookies and history" or a similar option, then follow the prompts.

Adjust device settings or usage


Devices can get seriously bogged down by too many applications running. Try to be in the habit of shutting down programs that you're not using to free up memory on your computer. The same is true if you tend to keep several browser windows or tabs active at the same time. This can cause lags or other problems when browsing the internet, so close any extra tabs that you're not actively using.


If you have smart devices running around your home, try lowering the screen resolution on any devices with a screen to save even more bandwidth and guard against a slow internet connection.

5. Check your wiring

Finally, checking both indoor and outdoor wiring can help determine if there's a connection problem that needs attention, either with your home equipment or with the CenturyLink network.

Check all cords and cables for damage. Also check to make sure both ends of the cables are firmly plugged in. Sometimes in regular use, they can get pulled loose.

  1. The power cord (often black) should be plugged into a wall outlet and into the power port on the back of the modem. 

  2. The DSL cord (often green) should be firmly plugged into the green DSL port on back of the modem, with the other end plugged into a working phone jack (until it clicks). 

  3. The Ethernet cord (often yellow) should be plugged into one of the Ethernet ports on the back of the modem, with the other end plugged into your computer's Ethernet port. You can try a different port if your modem has multiple ports, as shown in the image.
C4000 DSL port and power
Modem ports

DSL and power ports on the back of the C4000LG

DSL and power ports on the back of the C3000A
The ports will be similar on any box or tower-style modem/router.

Do you have both internet and home phone service from CenturyLink?

If you have both internet and home phone service from CenturyLink, then you will need to put DSL filters on all landline phones in the house. This ensures that your internet signal doesn't interfere with your landline.

Phone plugging into filter (diagram)

Plug the phone cord into a filter and then into the wall jack

Note: If you have cordless phones, you only need to install a filter on the phone base that plugs in to the wall jack; no filters are needed on the cordless units that only plug into an electrical outlet.

Make sure you do not have a filter installed between the modem and the wall jack.

Modem plugging in with no filter (diagram)

The DSL cord from the modem to the jack should not have a filter

If you want to plug both your modem and your phone into the same wall jack, you can use a DSL splitter, as shown in the diagram below.

Splitter to plug DSL line and phone into same jack (diagram)

Use a DSL splitter to plug a phone and a modem into one wall jack

You can figure out if there's a connection problem inside or outside your home by testing your service at the network box (Network Interface Device or NID).

Tried everything and still need more speed?

If you've gone through the steps above, try running the internet speed test to find out your current download and upload speeds. To check what speed you are currently paying for, check your plan details in My CenturyLink


It's a good idea to run the test a few times to get an average. Most technicians recommend running the test on a computer plugged into your modem with an Ethernet cable. This will give you the most accurate picture of your service speed from the network to the modem. It can also be useful to compare the wired connection speed to your speed over WiFi. Finally, testing on multiple devices may give you a sense of whether a particular device is slower.

After running the speed test, which statement best describes your situation? Click below to see solutions.

If your internet is dropping or going out on a regular basis, or you are consistently getting slower internet connection speeds than you expect, then there may be a problem with the network or with the connection at your address. To get further help, there are two things you can do:

  1. Run the Service Troubleshooter to diagnose issues with your line. If needed, you can open a repair ticket and schedule a technician directly from the troubleshooter.

  2. Contact a support agent for additional troubleshooting help or to request repair. We are here to help you get the best performance possible for your service.

If you're testing close to your plan speed, but still struggle with lag times and other symptoms of low bandwidth, you may simply need faster service. In this case, you have two options:

Upgrade your service. Check to see if you can upgrade to a faster internet plan. Log in to My CenturyLink on the web or through the My CenturyLink app to find out whether a speed upgrade is available at your address. This will depend on which speed tiers are sold in your area. 

Add a second line. A popular option is to double your speed by adding a second internet line to your home. The second line can be used exclusively for gaming and streaming, remote work/learning, or whatever you want. This is a great solution when you've already optimized your connection as much as possible, or if a speed upgrade isn't available. 

Look into rural internet options. Rural areas often get slower speeds than urban centers. If you live in a rural area, read more about using fixed wireless internet through an antenna to improve performance.

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Related topic from our Discover blog: 4 tips to improve your internet speed

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