When was the last time you heard someone ask, “Do you have bandwidth to take on this project right now?”

The term “bandwidth” has become a bit of a business buzzword in the last few years. People use this term to describe how much time or human resources they have available. But, when was the last time you heard someone use this word to describe their internet connection? As in, “Do you have bandwidth to download this video right now?”

As internet connections and infrastructures have improved, “bandwidth” has largely become a non-issue for many web visitors. In this post we’ll revisit bandwidth and cover why its relevancy to web performance has changed over time.

What is Bandwidth?

Bandwidth indicates the net bit rate, or the maximum amount of data in bits that can be delivered in parallel through a network. Latency is the amount of time it takes for data to travel across the network, such as from a web server to your browser.

Both of those concepts are kind of abstract for most people, so it is helpful to use an analogy: Think of the internet as a series of tubes with data flowing like water through those tube. The diameter of a tube is the bandwidth. The wider it is, the more water/data can pass through it in a given period of time. Latency is the length of the tube. The longer the tube/latency, the longer it takes for data to travel from one place to another.



Why is Bandwidth Important?

In the past, small bandwidths made it difficult to receive large packages of data. Now most web visitors in the US have access to broadband, or connections with bandwidth high enough to send large quantities of data in parallel. Meanwhile, the distance or latency between servers and devices remains the same. It still takes time to move that data from point A to point B. Latency can account for 90 – 95% of the time for downloading a request. This is why we must depend on solutions such as content delivery networks (CDNs). CDNs help reduce the distance between servers and devices so that content can be delivered more quickly.

While over 85% of the US has internet connection greater than 4 Mbps, this isn’t true for all countries worldwide.  If you’re serving your site to web visitors that do not have access to connections with large bandwidth then it’s even more critical that you prioritize web performance optimization in your website’s design and development.

Note: If you’re not sure about the bandwidth in a specific region, this is a great resource that pulls together useful data about connection speeds by country.

How Can I Test Bandwidth and Latency?

There are many free tools online that can help you test your bandwidth and latency. Most internet connections have different amounts of bandwidth devoted to uploading and downloading. This is why you may different Upload speed and Download speed.

It’s important to note that bandwidth is the theoretical maximum amount of bits that can be delivered through a network. Download Speed is how many bits you can actually download per second, and this could be dependent on how many other users are on your network.

One of the most popular tools for measuring download speed is Speedtest.net:

To use SpeedTest, open the URL in your browser and click
‘Begin Test.’ The tool will first look to see how many bits your connection can download per second, and then how many bits your connection can upload per second. SpeedTest also measures something called “Ping” which is really the latency; this is the amount of time it takes to transfer data to another computer on the network.

Snapshot from Speedpage.net test.


When it comes to optimizing the web performance of your site, latency and page size are more important than bandwidth. You may not be able to control a single user’s internet connection, but you can control how close your content is to your user and how much content you ask your visitor to download.

If you know that your visitors are coming from networks with low bandwidth, it’s even more important that you design responsibility with that in mind. Make trade-offs. Reduce rich content and serve the minimum-necessary elements to provide a functional experience to your visitors.