## TL;DR

The free online speed tests with the least bias is SpeedOf.Me with a bias of -0.4% (and a standard deviation of 0.1Mbps).

The advice above is based on a comprehensive test as described below.

## Contents

- Introduction
- Declaration of Interest
- What is the best?
- Method of measurement
- Speed tests to test
- The results
- Conclusions
- Other findings

## Introduction

Based on previous speed test tests (2020 and 2020 updated) I know the real internet speed I have and the factors that influence a speed test.

In addition, I know that the bias of a speed test is the most important factor to test. Therefore, this speed test only focuses on the biases of the speed tests.

## Declaration of Interest

In the past I (Hans van der Graaf) programmed my own speed test Internet Speed at a Glance. This because I was often not interested in the exact internet speed. Usually I want a quick indication if there are any problems with the internet connection.

In this speed test test I will treat Internet Speed at a Glance like all other speed tests being tested.

## What is the best?

For this speed test test, it is assumed that the best speed test has the lowest bias.

## Method of measurement

Based on an earlier tests, I know that the real internet speed I have is 84Mbps (the ISP used has increased the download speed from 50 to 75 Mbps in 2021).

Each speed test is tested at least 5 times with a clean browser on a wired Linux desktop.

The bias is calculated using the formula: bias = median - expected value, where the expected value is 84Mbps.

## Speed tests to test

For this speed test test this list of unique speed tests will be used.

## The results

The following has been measured (and calculated). Note that all values in Mbps.

- Bandwidth Place 70.00, 69.91, 69.91, 70.00, 70.08. Standard deviation: 0.07, median:70.00 bias: -14.00
- Broadband Internet Speed test (Gone) No meaningful results
- Broadband Speed Checker 74.83, 74.95, 74.85, 74.41, 75.00. Standard deviation: 0.23, median:74.85 bias: -9.15
- Cloudflare 75.4, 75.2, 75.5, 75.1, 75.4. Standard deviation: 0.2, median:75.4 bias: -8.6
- Comparitech 78.68, 81.30, 81.09, 80.89, 82.54. Standard deviation: 1.40, median:81.09 bias: -2.91
- DSLReports 75.2, 75.1, 73.8, 76.6, 76.3. Standard deviation: 1.1, median:75.2 bias: -8.8
- Fast 76, 63, 64, 52, 69. Standard deviation: 9, median:64bias: -20
- Fireprobe 76.18, 76.43, 76.16, 76.38, 76.25. Standard deviation: 0.12, median:76.25 bias: -7.75
- Google Fiber 76.1, 76.4, 76.4, 75.9, 76.4. Standard deviation: 0.2, median:76.4 bias: -7.6
- Internet Speed at a Glance 50..100, 50..100, 50..100, 50..100, 50..100. Standard deviation: -, median:- bias: -
- LibreSpeed 80.2, 81.0, 80.7, 80.8, 80.8. Standard deviation: 0.3, median:80.8 bias: -3.2
- Measurement Lab 75.96, 76.05, 75.87, 76.56, 76.10. Standard deviation: 0.27, median:76.05 bias: -7.95
- Meter.net 75.05, 74.86, 74.98, 74.72, 75.24. Standard deviation: 0.20, median:74.98 bias: -9.02
- N Perf 77.22, 77.11, 77.37, 77.66, 77.38. Standard deviation: 0.21, median:77.37 bias: -6.63
- Ookla Speedtest 74.29, 73.52, 74.23, 74.02, 74.50. Standard deviation: 0.37, median:74.23 bias: -9.77
- Open Speed Test 79.26, 79.38, 79.19, 78.11, 79.45. Standard deviation: 0.55, median:79.26 bias: -4.74
- RCN Speedtest (now redirected to Astound) 77, 77, 65, 77, 77. Standard deviation: 5, median:77 bias: -7
- SamKnows 76.4, 76.4, 76.4, 76.4, 76.4. Standard deviation: 0.0, median:76.4 bias: -7.6
- SpeedOf.me 83.44, 83.52, 83.50, 83.42, 83.52. Standard deviation: 0.05, median:83.50 bias: -0.50
- SpeedSmart 81.61, 79.23, 76.25, 78.31, 78.56. Standard deviation: 1.93, median:78.56 bias: -5.44
- Speedtest4.PHP No meaningful results
- TestMy.net 77.3, 76.9, 77.1, 76.8, 76.7. Standard deviation: 0.2, median:76.9 bias: -7.1
- Toast 53.2, 71.2, 71.8, 71.5, 70.7. Standard deviation: 8.1, median:71.2 bias: -12.8
- Xfinity xFi Speed Test 82.7, 79.2, 77.9, 77.2, 79.5. Standard deviation: 2.1, median:79.2 bias: -4.8

Previously I concluded that the max value of SpeedOf.me was most accurate. Hence I also measured these values:

- SpeedOf.me max 83.48, 83.52, 83.55, 83.52, 83.53. Standard deviation: 0.03, median:83.52 bias: -0.48

## Conclusions

Based on the above research, these are the speed tests with the least bias:

Note that taking in account the results of the 2020 speed test tests gives the following results:

The most consistent speed tests are:

## Other findings

Based on the above test and a comparison with the results of previous speed tests, the following can be concluded:

- Every speed test has a negative bias.
- Since almost every ISP vendor uses or recommends an Ookla-based speed test and the fact that the Ookla Speedtest has a negative bias of -10.5%, I can only conclude that the ISPs have agreed to provide a 12% higher bandwidth than what is advertised.
- When the Chromium browser is throtteld at 30Mbps, the real download speed is 34.0Mbps
- When the Firefox browser is throtteld at 30Mbps (Wi-Fi), the real download speed is 34.4Mbps