TL;DR
Initially, three categories of speed tests were distinguished. Later, two minor categories (ambiguous and miscellaneous) were added.
Realistic speed tests
A realistic speed test gives an indication of the true internet speed provided by your ISP.
A speed test is considered as a realistic speed test when the measured internet speed is 109-112% of the advertised speed.
Mainstream speed tests
A mainstream speed test gives test results that are close to the advertised speed. That is the measured internet speed is 100-103% of the advertised speed.
Conservative speedtests
Conservative speedtests measure structural an internet speed lower than the advertised speed.
Ambiguous speedtests
Ambiguous speedtests are speed tests of which the results are 104-108% of the advertised speed.
Miscellaneous speedtests
The last category of speed tests are speed tests that doesn't match criteria mentioned in which speed tests to test.
Speed test categorized
Each speed test has been tested multiple times with different advertised speeds (50, 75 and 100 Mbps). This makes it possible to calculate the average deviation from the advertised speed. This is then the basis for the categorization of the speed tests.
The overview below shows the average per category plus the values at 50, 75 and 100 Mbps between brackets.
Realistic speed tests
- Internet Speed at a Glance NA
- SpeedOf.Me 112% (112%, 111%, 112%)
- SpeedOf.me API Sample Page 111% (NA, NA, 111%)
- Comparitech 109% (108%, 108%, 110%)
Ambiguous speed tests
- Open Speed Test 106% (106%, 106%, 106%)
- Speedsmart 106% (109%, 105%, 103%)
- Xfinity xFi Speed Test 104% (102%, 106%, 105%)
Mainstream speed tests
- Fireprobe ® 102% (101%, 102%, 102%)
- Google Fiber 102% (101%, 102%, 102%)
- TestMy.net 102% (102%, 103%, 102%)
- Measurement Lab 101% (101%, 101%, 102%)
- Meter.net 100% (NA, 99%, 102%)
- Ookla Speedtest 100% (99%, 99%, 102%)
- Cloudflare 99% (96%, 101%, 101%)
Conservative speed tests
- Bandwidth Place 91% (95%, 93%, 86%)
- Fast 84% (80%, 85%, 87%)
Miscellaneous speedtests
All speed tests not mentioned above.