The quick way most people should use
The fastest way to check for packet loss is the ping command, which is built into Windows, Mac, and Linux without needing to install anything. Ping sends a series of small test packets to a destination and reports back how many made it. If you send 100 packets and only 97 reply, you have 3% packet loss on that route.
On Windows, open Command Prompt by typing cmd in the search bar, then type ping -n 100 google.com and press enter. On Mac or Linux, open Terminal and type ping -c 100 google.com. The test takes about a minute and a half to run. At the end you’ll see a summary line that tells you how many packets were sent, how many were received, and the packet loss percentage. That single number is what you’re looking for.
Run the test against a few different targets. Pinging google.com tests the full route to the internet. Pinging your own router (usually 192.168.1.1 or 192.168.0.1) tests only the connection inside your home. If loss shows up against Google but your router is clean, the problem is somewhere beyond your house. If your own router shows loss, the issue is in your home network.
The deeper test that shows where the loss is
Traceroute is the tool that actually pinpoints which piece of equipment is dropping your packets. Where ping just tells you that loss exists, traceroute shows you exactly where along the route it’s happening. This is the difference between knowing your car is making a noise and knowing which wheel it’s coming from.
On Windows, type tracert google.com. On Mac or Linux, type traceroute google.com. You’ll see a numbered list of hops, each one a router your packets pass through on their way to the destination. The first hop is your own router. The next few are your ISP. After that you cross into the wider internet. Each hop shows a response time and any packet loss at that point.
For a more accurate version of the same thing, install a free tool called PingPlotter or use the built-in MTR command on Mac and Linux (mtr google.com). These run the traceroute continuously and give you a live, easy to read view of where loss is appearing over time, which is far more useful than a single snapshot.
Tools for non-technical users
If the command line isn’t your thing, there are simpler options. Packetlosstest.com runs a browser-based test that takes about a minute and gives you a single clean number at the end. Speedtest.net by Ookla now includes packet loss in its results as well, which makes it easy to check alongside your usual speed test.
For ongoing monitoring rather than one-off testing, tools like PingPlotter (free for basic use) let you leave a test running in the background for hours or days. This is invaluable when the loss is intermittent, like only happening for ten minutes every evening, because you can’t catch it with a single quick test. Having a long log of when loss appears and where it appears is also exactly the kind of evidence that gets an ISP to take a complaint seriously.
Whatever tool you use, test at different times of day. A connection that’s clean at 10am but losing 4% at 9pm is telling you something specific about peak-time congestion that a one-off morning test would completely miss.