Why mobile speed tests differ from desktop
When you run a speed test on your phone, you are measuring the wireless connection between your phone's antenna and either your WiFi router or the nearest cellular tower. This introduces variables that desktop tests rarely encounter: signal strength fluctuates as you move, walls and furniture absorb radio waves, and your phone's antenna is smaller and less powerful than a laptop's.
iPhones and Android phones also manage network connections differently in the background. iOS aggressively manages WiFi connections to preserve battery, sometimes throttling network activity for apps running in the foreground. Android devices vary by manufacturer, with some applying battery optimisation that limits sustained network throughput during speed tests.
The most common mistake people make is testing while walking around or with the phone in a pocket. Your body absorbs radio signals and significantly reduces WiFi and cellular reception. For an accurate test, hold the phone in your hand in a stationary position with a clear line of sight to your router (for WiFi tests) or a window (for cellular tests).
Testing WiFi vs cellular speed
Before running a test, decide whether you are measuring your home WiFi or your mobile carrier's speed. If you want to test WiFi, make sure your phone is connected to your home network and that the cellular data toggle is off. If you want to test your carrier's 4G or 5G speed, disconnect from WiFi entirely.
For WiFi tests, stand within three metres of your router for the most accurate baseline. This eliminates signal degradation and gives you the best possible result your phone can achieve on your network. Then test from your normal usage locations (desk, couch, bedroom) to see the real-world speed drop caused by distance and obstacles.
For cellular tests, results will vary dramatically based on time of day, distance from the nearest tower, and the number of other users on that tower. Test at multiple times (morning, midday, evening) and in multiple locations. A single cellular speed test is almost meaningless — you need at least five measurements to establish a pattern.
Best practices for accurate mobile tests
Close all other apps before testing. Streaming services, social media apps, and cloud backup processes consume bandwidth in the background and will lower your speed test result. On iPhone, swipe up to see the app switcher and close everything. On Android, use the recent apps button to clear running applications.
Disable any VPN before testing. VPNs route your traffic through an additional server, adding latency and reducing throughput. The speed test result with a VPN active shows the speed of the VPN tunnel, not your actual internet connection.
Run the test at InternetSpeedTest.fit in your mobile browser rather than installing a separate app. Browser-based tests avoid app-specific quirks, require no permissions, and provide your Internet Fitness Score alongside raw metrics. The test automatically selects the closest server and runs download, upload, and latency measurements in sequence.