When testing your internet speed, you may have noticed that the numbers reported can vary quite a bit. Internet Service Providers quote a speed, but if you read carefully you'll notice the phrase "up to", which tells you that's just the maximum possible speed they can give. There are many factors that can contribute to the speeds you actually will get.
- Fluctuating speeds from the cable company
- Fluctuating speeds in your home
- Fluctuating speeds from device to device
- Bandwidth shaping on the network
- Testing your internet speed
- Interpreting your speed results
First of all, the service provided by your ISP will be inconsistent depending on how much bandwidth is being used by other customers. Imagine that your ISP has a big pipe that makes up their total amount of internet access that comes into the premisis. That pipe is connected to a switch that divies out that bandwidth to customers. This means the speed will fluctuate depending on how much bandwidth everyone is using at that time. This is less noticeable with DSL connections, because in most cases, the connection is from a switch at the phone company. With cable providers, however, there's a box in each neighborhood that offers a portion of that total bandwidth. This means internet access is shared amongst all of the customers in that area. You may have noticed that your speeds are down at peak times, like in the evenings when everyone is streaming Netflix.
The other cause of fluctuation is locally, in your own home. This is exactly the same problem as described above, but instead of the bandwidth being shared by neighbors, it's being shared by users in the house.
Another thing that impacts your speed is the speed of the device you're using. Internet mostly comes from Wi-Fi these days, and the Wi-Fi radios in your computers, tablets, and phones are not all made equal. You may find that the speeds are dramatically different from one phone to another, or on different computers. This comes down to hardware differences, but it can also be the operating systems used.
Newer routers, including the new mesh offerings from Eero, Netgear, Plume, Google, and more, take a 'smarter' approach to delivering internet access. They do something called "bandwidth shaping." This means your router is analyzing how the internet is being used so that it can offer the proper amount of speed for each activity. For instance, if someone is just using email, it can offer less bandwidth than another user who's streaming video.
All of these variables make it very difficult to get a good picture of what your internet speed is, but using the speed test sites online can help. Here are a few that are good to run:
Running these tests multiple times through the day can give you a general idea of what your speeds are like on average.
Download speed is the most important metric, since the majority of your usage is most likely consuming content, with streaming high definition and 4K video being the most taxing. But your upload speed is relevant as well, and can actually impact your download speeds. Whenever you upload something to the internet, each packet you upload needs a packet in return to download. This means it's easy to saturate the upload speed, making downloads nearly impossible.
Latency and jitter are also important results to check. Latency is the amount of time it takes to send a single packet to the server and back. A lot of latency can cause problems with gaming and making calls over the internet.