The Sherlock Holmes of Bandwidth
It’s frustrating. You pay for 500Mbps, but in the evenings, you get 50Mbps. Is it malice or incompetence?
Test 1: The VPN Check
Run a speed test. Then, turn on a trusted VPN (like Mullvad or Proton) and run it again.
- If speed INCREASES with VPN: You are being Throttled. Your ISP detected high traffic (like a download) and artificially slowed it down. The VPN hid the traffic type, bypassing the throttle.
- If speed stays SLOW: It is Congestion. The physical cables in your neighborhood are saturated. A VPN cannot fix a traffic jam.
What to do about Congestion?
Complaint. Call your ISP. Complain to the FCC (in the US). Congestion means they oversold your node.
The Split Test Method
The fastest way to distinguish throttling from congestion: test your speeds using two different speed test services back-to-back. ISPs that throttle specific services (like video streaming) often exempt speed test traffic to avoid detection. So run Ookla (which many ISPs whitelist from throttling), then immediately run Fast.com (Netflix’s speed test, which uses actual Netflix infrastructure). A significant gap — say, 200 Mbps on Ookla vs 30 Mbps on Fast.com — is a textbook sign of targeted throttling rather than general network congestion. Use a VPN to confirm: if your speeds equalize when encrypted, throttling is confirmed.
Frequently Asked Questions
How can I tell if my ISP is throttling me vs just having slow service?
Three diagnostic steps: (1) Test at different times of day — congestion follows peak-hour patterns (worst 7-10 PM), while throttling is consistent regardless of time. (2) Test with and without a VPN — throttling targets unencrypted traffic by protocol or destination, so a VPN often bypasses it. (3) Test different services — if Netflix is slow but YouTube is fast (or vice versa), the bottleneck is targeted, not general. All three confirming the same pattern is strong evidence of deliberate throttling.
What should I do after confirming my ISP is throttling me?
Document it with timestamps and test results, then contact your ISP’s support with the data. In the US, you can file a complaint with the FCC’s Consumer Complaint Center. Some state attorneys general have been active in pursuing throttling violations under consumer protection law. If your ISP is violating net neutrality protections active in your state, a formal complaint with documented evidence can result in a credit or service adjustment.