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What is Traceroute?

Traceroute (also called tracert on Windows, or tracepath on Linux) is a network diagnostic tool that maps the route your data takes across a TCP/IP network to reach its destination on the internet. When you load a website, your data doesn’t travel in a straight line. It hops through a series of routers, often across multiple cities or countries, before arriving. Traceroute reveals exactly what that path looks like, and how long each hop takes.

Here’s how it works: traceroute sends out small packets of data with a built-in countdown timer. Each router along the route decrements that timer by one. When it hits zero, the router sends back a signal identifying itself and traceroute logs its IP address and response time. Repeat that process across every hop in the chain, and you get a complete map of the route your data traveled, measured in milliseconds per hop.

That map is genuinely useful when something goes wrong. If a website is slow or unreachable, a traceroute can show you exactly where in the chain the delay or failure is happening, whether that’s on your local network, with your internet service provider (ISP), or somewhere further down the line. It’s also worth knowing that hackers have historically used traceroute to map network infrastructure before launching attacks, which is why some networks block it entirely. Seeing a hop return asterisks instead of a response time usually means that that router is configured not to reply, not necessarily that something is broken.

You can run a traceroute directly from your device using the command line, or use a traceroute tool to get results alongside geographic location data for each hop.