This is a genuinely useful diagnostic starting point: if your router and internet plan were the problem, every device would be affected equally. One slow device while everything else is normal points specifically to something on that machine — its WiFi adapter, drivers, background usage, or its specific connection to the router.
Step 1: confirm with an actual speed test
Run a speed test (e.g., fast.com or speedtest.net) on both the slow device and a working device, ideally at roughly the same time, to get a real number comparison rather than relying on a general impression of "feels slow."
Fix 1: check for background bandwidth usage on the slow device
Often the simplest explanation: something on that specific computer is consuming bandwidth in the background without your awareness:
- Check for Windows Updates downloading, OneDrive doing a large sync, or a cloud backup running
- Open Task Manager → Performance tab → check the Ethernet/WiFi usage graph for unexpected activity
- Check for any apps you forgot were open and actively streaming/downloading/uploading
Fix 2: check WiFi signal strength and band
If this device is further from the router than others, or connected to a different (often more congested) WiFi band:
- Check the WiFi signal icon for this device specifically — if it shows weak signal while other devices show strong, distance or obstruction is likely the cause
- If your router broadcasts separate 2.4GHz and 5GHz networks, check which one this device is connected to — 5GHz is generally faster but has shorter range; 2.4GHz reaches further but is often more congested and slower. If this device ended up on a different band than your faster devices, that alone can explain a real difference.
Fix 3: update the WiFi adapter driver
An outdated or generic driver can genuinely cap your real-world speed below what the hardware is capable of, even with a strong signal:
- Visit your laptop or WiFi adapter manufacturer's website and download the latest driver for your specific model
- Install and restart
Fix 4: check for a wired connection capped lower than expected
If this is a desktop connected via Ethernet rather than WiFi, check the actual negotiated link speed:
- Go to Settings → Network & internet → Ethernet, click your connection
- Check the reported link speed — if it shows something like 100 Mbps when your plan and cable should support 1 Gbps, this points to either an older/damaged cable or a port issue, worth testing with a different cable
Fix 5: test with WiFi adapter power management disabled
Similar to the disconnection issue, power-saving settings can throttle a WiFi adapter's performance, not just cause outright disconnects: Device Manager → Network adapters → your WiFi adapter → Properties → Power Management tab, uncheck "Allow the computer to turn off this device to save power."
If none of the above explains it
If this is an older device with an aging WiFi adapter, it may genuinely be hardware-limited compared to newer devices on the same network, especially for newer, faster WiFi standards your router might support that an older adapter simply can't take advantage of. In that case, a USB WiFi adapter upgrade is a relatively inexpensive way to bring an older computer's wireless performance closer to modern devices without replacing the whole machine.