Why Is My Internet Slow?
Slow internet has 14 distinct causes — from ISP peak-hour congestion and router bufferbloat to WiFi interference, DNS slowdowns and background software. Use our free 8-step diagnostic checklist and browser-based tools to find the exact bottleneck and fix it without calling your ISP.
Common causes of slow internet
| Cause | Typical clue |
|---|---|
| ISP peak-hour congestion | 30%+ drop 6–11 PM vs morning |
| ISP throttling | Speed test looks fine; Netflix or games still stall |
| Router bufferbloat | Ping jumps when anyone downloads |
| WiFi distance / walls | Ethernet is fast; phones in other rooms are not |
| Channel congestion | Many neighbor networks on the same channel |
| Slow DNS | Pages feel sluggish even when Mbps is high |
| Background updates | One PC saturates the line |
| Old router hardware | Plan is 500 Mbps; you never see above ~150 |
Start with a speed test, then bufferbloat and throttling if Mbps looks fine but the connection still feels slow.
Frequently Asked Questions
Why is my internet slow all of a sudden?
Sudden slowness is usually ISP congestion, a router that needs a restart, a background update, or a crowded WiFi channel. Restart the router, then run a speed test morning versus evening.
Why is WiFi slow but Ethernet is fast?
The wireless hop is the problem: distance, walls, channel congestion or an old adapter. Switch to 5 GHz or Ethernet.
Why is my internet slow only in the evening?
Peak-hour congestion on shared cable or DSL is the usual cause. Compare 8 AM versus 8 PM results.