What Is Latency?


Latency is the amount of time that it takes for a signal to travel from your computer to a remote server (such as the physical machine where Netflix stores its video) and back. It’s a factor in everyone’s online experience, but most people are less familiar with it than they are with other measures of internet speed, like bandwidth. Latency is also not something that most internet service providers (ISPs) advertise, so even if you want a low-latency connection, it can be hard to know where to look.

If this is sounding a lot like “internet speed,” you’re not entirely wrong. Both bandwidth (or download speed) and latency look at how fast data is moving across a network, but they each measure different things and have very different effects on your online experience.

Don’t worry, we’re here to help you answer all your questions about internet speed and latency so that you can get the most out of your internet connection.

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What’s the difference between Latency and Bandwidth?

Bandwidth, or download speed, is what most ISPs advertise on their plans. If you have a 100 Mbps internet connection, that means that your download speed is 100 Mbps. Download speed tells you how long it takes for a certain amount of data from the internet to reach your computer.

If we think of data like water, your bandwidth is the size of the pipe leading to your house. A wider pipe can carry more water, and fill up a pool faster. The water doesn’t necessarily move faster down a wider pipe, there’s just more of it.

Latency measures how long it takes for a specific piece of data to reach your computer, and is measured in milliseconds (ms). You can test your latency by sending a single “ping” of information to a remote server and timing how long it takes until that signal comes back. This is why latency is often referred to as “ping” or “ping rate.”

If bandwidth is the width of the pipe filling up your pool, latency would be the length of the pipe. If you have a really long pipe, there will be a delay between when you turn the water on and when it actually starts flowing out of the end of the pipe. This usually won’t have a huge impact on how long it takes to fill a pool, but if you were filling a series of smaller buckets and had to turn the water on and off between each one, it would become pretty inconvenient.

Although connections with a faster download speed usually have lower latency (and the two are interrelated), that’s not always the case. Satellite connections, for instance, have very high latency but can also have higher download speeds than many other plans. If you tried to download the same 1 GB file over a 10 Mbps DSL connection and a 100 Mbps satellite connection, the DSL line would get a big head start due to its lower latency, but the satellite connection would still get the file more quickly. A bigger pipe will fill up your pool faster than a smaller one, even if the water has to travel a bit longer to get there.

What types of connections have low latency?

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Connection typeDownload speedsLatency1
Fiber50–2,000 Mbps (2 Gbps)11–14 ms
Cable15–1,000 Mbps (1 Gbps)15–35 ms
DSL1–100 Mbps25–43 ms
Satellite12–100 Mbps594–624 ms

Wired connections generally have the lowest latency, with fiber being the lowest of them all. Satellite internet has extremely high latency, due to the distance between satellites and the surface of the Earth. (Though low-Earth orbit satellite constellations like Starlink could offer much lower latency connections.)

Other wireless technologies generally have more latency than wired connections, but still manage to keep it below 100 ms, which is good for activities like online multiplayer games. 5G connections might even be able to get latency as low as many wired connections, making it another good option for playing online games.

What determines latency?

Latency is determined by several factors, including these:

  • Distance
  • Transmission medium
  • Number of network devices
  • Network congestion

Every internet connection has to deal with one fixed time cost: distance. Even data traveling at the speed of light takes longer to reach a server based in Australia than one a few blocks away. No matter how much you optimize your network, you can’t escape these physical limits. This is why satellite internet, which has to send its signal into space and back, will always have to deal with more latency than other types of connections.

Data also travels at different speeds along different transmission media. Fiber optic cable is among the fastest, but light traveling through a fiber optic cable is still slower than light traveling through a vacuum. Copper wire, unsurprisingly, transmits information much slower than fiber optic cable.

In addition to delays from distance, the more devices your information passes through, the longer it takes to arrive. Your computer doesn’t have a direct line connecting it to the server you’re trying to access. Instead, it must cross multiple networks to arrive at its destination.

These networks are connected at internet exchange points, which function like giant routers. Every packet that these devices receive must be examined and then sent in the right direction, which causes additional delays (known as propagation delays). Signals also must be boosted by repeaters the farther they travel, which can introduce even more delays.

Network congestion can also cause delays. If a device on a network has more data passing through it than it can handle, this creates a bottleneck, creating delays as your data packets wait their turn.

When does latency matter?

Latency has an impact on the overall speed of your internet connection, but many applications have found ways to get around it. Video services like Netflix, for example, buffer the data they download. This means that they get ahead of the playback and store extra video data so that it’s ready to go as soon as it’s needed. Even if there’s a delay or a sudden fluctuation in the stream, the video can still playback smoothly as long as there’s still information in the buffer.

Other types of activities are less forgiving. Online games rely on two-way interaction between the player and the server. Latency slows down your reaction time, also known as lag. Lag can make your actions sluggish or shaky. If your latency gets too high, you can be dropped from the game altogether.

Swipe left to see all →
Latency matters a littleLatency matters a lot
Streaming videoOnline multiplayer games
Downloading filesLive video
Web surfingVideo chat

In general, activities that require real-time interaction suffer the most from high latency, while other activities won’t be noticeably affected. All they need to run smoothly is a good internet speed.

What is a good amount of latency?

A good amount of latency is between 50 and 100 ms. This is a fast enough response time for fast-paced online multiplayer games and near instantaneous interaction over video chat. Latency over 100 ms is usually when players start experiencing noticeable lag in online games. If your latency is over 150 ms, lag can become serious enough to get you dropped from a game and could cause very noticeable glitches in a live video chat.

While it’s pretty much impossible to play a game like Fortnite on a high-latency connection, there are games with much more leisurely paces that work just fine. For some good examples, check out our guide to gaming on satellite internet.

How do I reduce latency?

Although you can never completely eliminate latency, you can take steps to reduce it. First, plug your device directly into the router using an ethernet cable, rather than using your Wi-Fi network. Even if you have a really good router, taking the information coming into your router and rebroadcasting it over your Wi-Fi network is one extra step along the way that adds a few milliseconds to your latency.

Next, make sure that the drivers on your router and other network devices are up to date. This makes sure information gets processed and passed along as efficiently as possible, minimizing extra delay. You can also update the drivers on your computer or laptop to ensure that it’s connecting to the network efficiently.

If you’re still getting too much latency on your connection, it might be time to upgrade your internet connection.

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Sources

  1. Federal Communications Commission, “Seventh Measuring Broadband America Fixed Broadband Report: Appendix F-1,” May 20, 2011. Accessed December 16, 2020.
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