I've tried a bunch of broadband speed tests. Up until the last year or so, they usually agreed fairly closely when measuring my connection. Recently, the reported speeds have been much more diverse. I've read that Flash-based tests are all currently unreliable due to technical limitations in the current versions of Flash, so I've been trying non-Flash tests as well, but the results are inconclusive.
Why do the results vary so much? Is my ISP gaming the results of speed tests somehow? Is there a truly accurate test out there? I'd like to be able to say to my ISP that "test X is known to be accurate and it shows my speed is less than it should be."
Here are some of the results I've gotten recently, on a Shaw Cable plan in Canada (25 Mbps down; 2.5 Mbps up) (all speeds in Mbps - Down / Up):
- Speedtest.net (Flash): 24.27 / 2.37
- NCSI Netalyzer (Java): >20 / 2.4
- TestMy.net (HTML5/PHP): 3.5 / 2.1
- SpeedOf.me (HTML5): 9.03 / 2.55
- BandwidthPlace (HTML5): 2.4 / 2.25
- AuditMyPC (Java): 31.7 / 2.61
- Shaw's speed test (Flash): 22.94 / 2.21
- Speedguide.net (PHP): 3.54 / 2.22
- Speed.io (Flash): 23.42 / 0.59
- Speakeasy (Flash): 9.32 / 2.29
- Internet Frog (Flash): 5.38 / 1.61
- DSLReports speed test (Flash): 3.81 / 1.95