How do I diagnose not being able to reach a specific website as an end user?

If I can generally reach web pages on the Internet but can't reach a specific one, how do I troubleshoot what the cause is as an end user?

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Solution 1:

Maybe the website is actually down.

Try visiting http://downforeveryoneorjustme.com.

If it says "It's not just you" the website is likely having an outage and you should try to report it if possible -- or just wait.

Maybe it's a DNS problem.

See if the website DNS name (let's say it is example.com) resolves to an IP address. You can do this by starting a console or command prompt, and typing ping example.com

C:\Users\Jeff>ping example.com

Pinging example.com [192.0.32.10] with 32 bytes of data:
Reply from 192.0.32.10: bytes=32 time=26ms TTL=244
Reply from 192.0.32.10: bytes=32 time=27ms TTL=244
Reply from 192.0.32.10: bytes=32 time=27ms TTL=244
Reply from 192.0.32.10: bytes=32 time=39ms TTL=244

Ping statistics for 192.0.32.10:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 26ms, Maximum = 39ms, Average = 29ms

If you get an "unknown host" error this means there is likely a DNS problem. You can try seeing if it resolves against Google's DNS with nslookup stackoverflow.com 8.8.8.8.

C:\Users\Jeff>nslookup example.com 8.8.8.8
Server:  google-public-dns-a.google.com
Address:  8.8.8.8

Non-authoritative answer:
Name:    example.com
Addresses:  2620:0:2d0:200::10
          192.0.32.10

If it does resolve with that command then you probably want to contact your DNS provider (likely your ISP). If you want to run further DNS tests, try GRC's DNS Benchmark for Windows, or the services just-ping.com and whatsmydns.net.

Maybe it's a browser problem.

If it does resolve in DNS, but you don't get ping replies it means they are either filtering pings or you can't reach that site. If you are getting replies you might have a browser or browser proxy issue. Try installing another web browser with all default settings and see if you get any different results.

Maybe it's a problem with your internet connection.

If it is resolving but you can't reach it try running tracert example.com and see where they start timing out.

Tracing route to example.com [192.0.32.10]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  192.168.1.1 
  2    15 ms    26 ms    29 ms  c-x-x-x-x.hsd1.ca.comcast.net [x.x.x.x] 
  3    10 ms    25 ms     9 ms  te-5-4-ur04.pinole.ca.sfba.comcast.net [68.86.248.169] 
  4    12 ms    13 ms    14 ms  te-0-6-0-0-ar01.oakland.ca.sfba.comcast.net [68.85.154.86] 
  5    35 ms    15 ms    12 ms  pos-0-3-0-0-cr01.sacramento.ca.ibone.comcast.net [68.86.90.129] 
  6    15 ms    16 ms    18 ms  pos-0-9-0-0-cr01.sanjose.ca.ibone.comcast.net [68.86.85.181] 
  7    16 ms    18 ms    19 ms  xe-11-1-0.edge1.SanJose1.Level3.net [4.79.43.133] 
  8    27 ms    18 ms    33 ms  vlan69.csw1.SanJose1.Level3.net [4.68.18.62] 
  9    77 ms    29 ms   183 ms  ae-63-63.ebr3.SanJose1.Level3.net [4.69.134.225] 
 10    28 ms    35 ms    35 ms  ae-2-2.ebr3.LosAngeles1.Level3.net [4.69.132.10] 
 11    43 ms    27 ms    60 ms  ae-31-80.car1.LosAngeles1.Level3.net [4.69.144.131] 
 12    23 ms    23 ms    28 ms  INTERNET-CO.car1.LosAngeles1.Level3.net [4.71.140.222] 
 13    24 ms    23 ms    24 ms  www.example.com [192.0.32.10] 

Trace complete.  

You can also try PingPlotter (Shareware; Free 30-day evaluation.) which will repeatedly run a traceroute and graph the results, so you can see if you have packet loss or bandwidth problems at any hop on the traceroute.

Let this run for a while. If it is timing out after only an entry or two you probably want to contact your internet service provider. If it is timing out towards the end you should contact the webmaster of the site, if possible. Whoever you contact, include the output of the ping and traceroute commands.

Solution 2:

Something else to look for is a faulty router.

I recently had this situation with accessing any Stack Exchange site. It would time out, return connection errors and generally "lock me out" for 5 minutes at a time. Virtually all other sites were OK.

After lengthy chats with Stack Exchange staff (very helpful) and my ISP I narrowed it down to the router. Swapping it out has apparently cured the problem.

The problem here (I think) was that what ever the fault was on the router it couldn't cope with the relatively high volume of traffic I was generating when using Stack Exchange as a logged in user with multiple accounts and having a lot of them visible at any one time.

The fact that only one site (well one set of sites) was affected led me to believe that the problem lie elsewhere.