Internet Speed & Latency Troubleshooting Tool
Isolate whether your speed bottleneck is inside your WiFi radio, a damaged Ethernet cable, router CPU/QoS limits, or your ISP's outside coaxial/fiber line.
Choose your primary symptom above and click Run Diagnostic Workflow.
How to Isolate ISP vs. Router vs. WiFi Bottlenecks
Running a browser speed test over WiFi from two rooms away tests your wireless environment, not your ISP speed. To pinpoint the exact bottleneck in under 10 minutes, compare three measurements:
- Direct Modem/ONT Wired Baseline: Plug a laptop with a verified Gigabit or 2.5GbE adapter directly into your cable modem or fiber ONT. If speed is still below 80% of your plan tier during off-peak hours, the issue is on your ISP's line or modem signal levels.
- Router LAN Wired Baseline: Plug the laptop into a LAN port on your router. If the modem was fast (e.g., 940 Mbps) but the router LAN port caps at 94 Mbps, either the WAN patch cord has a damaged pin (dropping the link to
100BASE-TX) or an old QoS bandwidth limiter is enabled in the router firmware. - Same-Room 5 GHz / 6 GHz WiFi Baseline: Test WiFi standing 6 feet from the router. If wired is 940 Mbps and WiFi is only 45 Mbps, your phone or laptop is stuck on the 2.4 GHz band instead of 5 GHz/6 GHz.
Speed Bottleneck Signature Reference Table
| Measured Speed Signature | Root Cause | Immediate Fix |
|---|---|---|
| Stuck at 90–95 Mbps (on a 300+ Mbps plan) | Physical link negotiated at 100 Mbps instead of 1000 Mbps | Replace the WAN/LAN Cat6 patch cable and check switch port LED colors |
| Stuck at 35–55 Mbps on WiFi (Wired is 500+ Mbps) | Client device connected to 20 MHz 2.4 GHz band | Enable band steering or connect to the 5 GHz / 6 GHz SSID (80 MHz width) |
| Fast download, but video calls freeze when someone uploads | Bufferbloat (unmanaged upstream modem/router queue) | Enable SQM (Cake / FQ_CoDel / Adaptive QoS) capped at 90% of true upload speed |
| Speed drops 80% only when VPN is turned on | Router CPU bottlenecked by single-threaded OpenVPN encryption | Switch router VPN protocol from OpenVPN to WireGuard |