You open a speed test website, click Go, and see a result of 100 Mbps. Your ISP promised 100 Mbps and you are getting it. But then a video call drops, a file download feels slow, and online games lag. What is going on?
The truth is — a single speed test result tells you very little about your real internet experience. Understanding what you are actually measuring and how to test correctly can save hours of frustration and help you accurately diagnose network problems.
What Does a Speed Test Actually Measure?
When you run a speed test, the tool measures the speed between your device and a remote server. It measures three things:
- Download speed — How fast data travels from the server to your device
- Upload speed — How fast data travels from your device to the server
- Ping / Latency — How long it takes for a signal to travel to the server and back (in milliseconds)
What it does NOT measure — your LAN speed, WiFi signal quality, router performance, cable condition, or speed to the specific servers you use daily.
The Big Problem — LAN Speed vs WAN Speed
This is the most misunderstood aspect of internet speed testing. There are two completely separate speeds in your network:
| Factor | LAN Speed | WAN Speed |
|---|---|---|
| What it is | Speed within your local network | Speed to the internet |
| Typical speed | 100 Mbps to 10 Gbps | 10 Mbps to 1 Gbps |
| Affected by | Cable quality, switch, router | ISP, time of day, server |
| Tested by | LAN speed test tools | Online speed test sites |
| Common issue | Bad cable, cheap switch | ISP throttling, congestion |
Why You Must Test LAN Speed First
Before blaming your ISP for slow internet, always test your LAN speed first. Here are three real-world scenarios:
Scenario 1 — The Bad Cable Problem
A customer has a 100 Mbps connection but gets only 20 Mbps on speed test. The ISP checks their end — full 100 Mbps is being delivered to the modem. The real problem? A damaged Ethernet cable between the modem and router. The cable is the bottleneck — not the ISP.
Scenario 2 — The WiFi Problem
A customer runs a speed test on their laptop over WiFi and gets 30 Mbps. Their plan is 100 Mbps. But when tested with a direct Ethernet cable, they get full 100 Mbps. The WiFi signal is weak due to distance or interference. Again — not the ISP's fault.
Scenario 3 — The Congestion Problem
A customer gets 80 Mbps in the morning but only 20 Mbps in the evening. Running the speed test at different times reveals this pattern — evening peak hours are causing network congestion. This may genuinely be an ISP issue.
Why Different Speed Test Sites Show Different Results
- Server location matters — A speed test to a server 500km away will show lower speed than one 10km away
- Server load varies — If the speed test server is busy, your result will be lower
- Different protocols — Some tools use HTTP, others use TCP or UDP which give different results
- ISP peering agreements — ISPs have direct high-speed connections to some networks and not others
- Time of day — Network congestion at peak hours (6pm–11pm) affects results significantly
"A speed test is a snapshot of your connection to one server at one moment in time. To understand your real internet performance, you need multiple tests to multiple servers at different times of day."
The Right Way to Test Your Internet Speed
Test LAN Speed First
Use a local network speed test tool between two devices on your network. This shows the maximum speed your local hardware can handle before any internet traffic is involved.
Connect via Ethernet — Not WiFi
Always run your WAN speed test with a direct Ethernet cable connected to your router. WiFi introduces variables that make results unreliable for diagnosing ISP issues.
Test at Multiple Times of Day
Run tests at morning (9am), afternoon (3pm) and evening (9pm). If evening speeds are consistently lower — network congestion is the likely cause.
Test to Multiple Servers
Use different speed test tools and select servers in different locations. A dramatic difference between nearby and distant servers indicates routing or peering issues.
Run 3 to 5 Tests and Average the Results
A single test can be affected by temporary congestion. Run multiple tests and note the average for a reliable result.
Close All Background Applications
Before testing, close all apps that use internet — cloud backups, Windows updates, streaming services. Any background usage will lower your speed test result.
Introducing OpenSpeedTest — Best Tool for Accurate Testing
OpenSpeedTest is a free, open-source speed testing tool that works directly in your browser with no plugins or downloads required. It is one of the most accurate and privacy-friendly speed test tools available and works for both LAN and WAN testing.
- ✓ Works on your local network — Can be deployed locally to test LAN speed accurately
- ✓ No Flash or plugins — Pure HTML5, works on all devices including mobile
- ✓ Open source — Transparent, no hidden data collection
- ✓ Self-hosted option — ISPs can deploy it on their own servers for accurate local testing
- ✓ Tests download, upload and latency — All three key metrics in one test
Test Your Speed Right Now
Use the embedded OpenSpeedTest below to check your current internet speed. For best results — connect via Ethernet cable and close all background applications before testing.
How to Test LAN Speed Using OpenSpeedTest
Method 1 — Using Docker (Recommended for ISPs)
Deploy OpenSpeedTest on a local server within your network:
docker run --restart=unless-stopped --name openspeedtest -d -p 3000:3000 openspeedtest/speed-testThen access it at http://YOUR-SERVER-IP:3000 from any device on your local network. This measures pure LAN speed without any internet involvement.
Method 2 — Two Device Testing
Run OpenSpeedTest on one device (server) and access it from another device (client) on the same network. The result shows exactly what speed your LAN hardware supports between those two points.
Understanding Your Speed Test Results
| Result | What It Means | Action |
|---|---|---|
| LAN fast, WAN slow | ISP or WAN hardware issue | Contact ISP with evidence |
| LAN slow, WAN normal | Local network problem | Check cables, switch, router |
| Both slow | Critical local network issue | Check all hardware systematically |
| WiFi slow, Ethernet fast | WiFi interference or range | Move router, change WiFi channel |
| Morning fast, Evening slow | Network congestion | Discuss with ISP about peak hours |
| All tests consistent | Healthy connection | No action needed |
Tips for ISPs — Educate Your Customers
- Provide your own speed test server — Deploy OpenSpeedTest on your network so customers test against your infrastructure directly
- Create a speed test page — Add a dedicated speed test page on your website using OpenSpeedTest embed
- Include testing instructions — Add a simple guide with your welcome kit explaining how to test correctly
- Document baseline speeds — Keep records of speed test results during installation for future reference
Conclusion
A single speed test result is like taking your temperature once and declaring yourself healthy forever. Network performance is dynamic — it changes based on time, load, hardware, and dozens of other factors.
- Always test LAN speed before WAN speed — local network issues are more common than ISP issues
- Use Ethernet cable for accurate WAN speed testing — WiFi introduces too many variables
- Test multiple times at different times of day and compare results
- Use OpenSpeedTest for accurate, unbiased and privacy-friendly speed testing
- A result lower than your plan speed is not always the ISP's fault — investigate systematically
Have questions about speed testing or network performance? Contact our team — we are always happy to help.