Why Does Comcast Internet Speed Fluctuate?

By Editorial Team

Updated September 09, 2022

Online gamers and TV watchers may notice speed fluctuations more than other users.
i Alistair Berg/DigitalVision/GettyImages

Comcast boasts fast internet speeds, but a variety of factors can affect the actual speeds you experience. From hardware to other users, Comcast internet speeds tend to fluctuate often. If you test your speed throughout the day, you'll notice faster and slower speeds. Advertised Comcast speeds are typically just an average or maximum and not a guarantee. With the right equipment, settings and software, you can optimize your speed and get the most from your service.

The Right Equipment Makes a Difference

You may be tempted to save money by buying the cheapest modem and router possible. However, Comcast internet speed is usually best when you use a Comcast-approved modem. Comcast provides a list of approved modems based upon your speed tier (see Resources). While you can use any router that supports any of the major three wireless standards (b, g and n), Comcast recommends using a router that is 802.11n capable, as those routers allow for the fastest speeds possible.

A Squeaky Clean PC Equals Faster Speeds

Factors such as viruses and a cluttered hard drive can cause Comcast speeds to fluctuate. Comcast's toolbar and Constant Guard service help prevent and remove spyware, malware and other viruses. However, you can use your own anti-virus program to scan and remove any viruses from your system.

The less space you have on your hard drive, the slower your computer can run, causing slower internet speeds. For best results, Comcast recommends running Windows Defrag and Scandisk at least once a month. The company also suggests clearing your internet cache to remove excess temporary internet files. If you have little space on your hard drive, consider deleting files you no longer need or moving some files to an external hard drive to free up space.

Update Your Browser To Improve Xfinity Internet Speed

Comcast works best on the latest browsers, according to Xfinity. If you're experiencing fluctuating speeds, updating your browser may help. Comcast suggests using the latest operating system as well. Install the latest updates for your operating system to optimize your computer and internet speeds.

Blame the Neighbors

While cable internet is designed to be fast, the network can get congested at times. If your speeds tend to slow down a specific times each day, the problem is simply too many people using Comcast at one time. The servers become bogged down and speeds slow for all users. If you need faster speeds for streaming or gaming, consider waiting until after peak usage times. Casual internet users may not notice any major lags due to peak usage times.

Break Down the Walls

If you have physical barriers between your router and computer, the barriers can cause speed issues, according to Xfinity. Large metal objects and walls can cause disruptions. To optimize your speeds, move your router to a more open area. If your router is near any type of appliance with the same wireless frequency, you may notice speed changes when those appliances are in use. Keep your router away from any objects that might interfere with the router's wireless signal.

Check for Loose Cables

Sometimes the problem is as simple as a loose or damaged cable. Check all your connections and cables to ensure everything is properly connected. A damaged outlet or a blown fuse can also be to blame. If the speed fluctuations begin suddenly, the problem may very well be a basic equipment issue.