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HowFast

Fiber speed test

Updated

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Fiber connections are fast in both directions and usually have low latency, so testing them well takes a little more care than testing cable or DSL. This guide explains what to expect and how to get a result that reflects your plan.

What to expect from fiber

  • Symmetric speeds. Many fiber plans (fiber to the home, FTTH) upload as fast as they download. If your upload is far below your download on a symmetric plan, something is limiting it.
  • Low latency. Idle latency to a nearby server is often between 5 and 20 ms on a cable connection.
  • Little bufferbloat. Fiber equipment often manages queues well, but not always. The bufferbloat grade shows whether calls and games stay smooth while the line is busy.
  • Fiber to the cabinet is different. Plans described as “fiber broadband” that use copper for the last stretch (FTTC or VDSL) behave more like DSL: lower upload and speed that falls with distance.

How to test a fiber connection properly

  1. Use a cable. Even good Wi-Fi rarely delivers more than a few hundred Mbps to a single device. Connect a computer to the router with an Ethernet cable.
  2. Check the port and cable. A gigabit plan needs a gigabit port (1 GbE) and a Cat5e or better cable. Plans above 1 Gbps need 2.5 GbE or faster ports on both the router and the computer.
  3. Use a capable device. Older laptops, USB adapters and low-power devices can top out well below gigabit speeds.
  4. Choose Detailed mode on plans of about 500 Mbps or more. It adds a four-connection test that shows what the line can carry in total, next to the single-connection headline.
  5. Close everything else and run the test two or three times.

Why a gigabit plan may read lower

  • One connection vs many. The headline figure is what a single browser connection achieves, because that is what most downloads and streams use. On very fast lines, one connection may not fill the pipe. The multi-connection figure in Detailed mode is the better comparison with your plan.
  • Overhead. Network protocols use part of the capacity, so about 940 Mbps is the practical maximum for data over a 1 Gbps link.
  • The browser and device. Speed tests in a browser depend on the device’s processor and the browser’s networking. Results above 1 Gbps are especially sensitive to this.
  • Wi-Fi. By far the most common reason fiber reads slow.

Reading your result

On a healthy fiber line, expect most activities to rate Great. If something doesn’t:

  • Upload holds back calls or large uploads: check whether your plan is symmetric, and test on a cable.
  • Bufferbloat grade C or worse: your router may not manage queues well under load. See bufferbloat.
  • Latency higher than expected: check for a VPN, Wi-Fi, or a distant test location shown on the Network card.

The methodology page explains how every number is measured.