When I open a question at stackoverflow.com it comes at a normal time (instantly or 1 second), but if I refresh the page by F5 I wait for about 5 seconds, sometimes more.

The browser status says: waiting for cdn.sstatic.net

Is there something wrong with the Content Delivery Network from sstatic.net?

enter image description here

I seems this is nothing with to do in a far location. From comments, users states the same issue from their location:

  • Oded: London England.
  • adarshr: England
  • mistaecko: SEA
  • cdeszaq: Madison, WI
  • Daniel Beck: Germany

Maybe europe users are redirected to specific cdn server then the server have congestion result: as seen in picture aboce 1KB downladed ~ in 1 second.

This speed is equal either 56K modem times or distance for a user at Mars.

As seen also aboce picture content from cdn.sstatic:

  • stub.js?v=18904b11d
  • all.css?v=713c09ff9631

served at the same time.

  • 2
    Your location, ISP, and bandwidth are probably helpful here. Reloading all the resources will take longer than a normal page load but 5 seconds seems high for "normal" conditions.
    – user154510
    Commented Jan 24, 2012 at 20:42
  • Yes, refreshing will reload the assets instead of using cached ones. Possibly they don't have a server near enough to your location.
    – user154510
    Commented Jan 24, 2012 at 20:47
  • I have seen this issue from London, England.
    – Oded
    Commented Jan 24, 2012 at 20:48
  • (As an aside: clicking links, like clicking the SO logo, does not make the browser ask the server if cached resources have changed, while reloading does. So if the CDN is slow and everyone uses refresh, and clicks refresh again if things are not fast enough, then that only makes things worse... Of course, this does not imply that the CDN should not respond promptly to start with.)
    – Arjan
    Commented Jan 24, 2012 at 20:50
  • Just to be sure: you're not to blame for using F5, of course. Still, it's odd (and too bad) that browsers then need to contact the servers even for the static resources, while actually they very well have been told they can cache that very same static content. I'm sure there is a good explanation why browser behave like that, but I've never found int.
    – Arjan
    Commented Jan 24, 2012 at 20:55
  • @Arjan: I think The Stack is doing something strange: StackExchange.using.setCacheBreakers({"js/prettify-full.js":"6c71f9dce92f","js/moderator.js":"723991e143f9",... I think they want the behavior you've described.
    – sarnold
    Commented Jan 24, 2012 at 23:46
  • No, @sarnold, the value used in the cache breakers does not change upon reloading (if all is well). It's just a way to ensure things are cleared when the site is updated.
    – Arjan
    Commented Jan 25, 2012 at 6:34
  • I had the same issue on Super User yesterday around the same time (a few related chat messages, screenshot Safari OS X, screenshot Chrome OS X). ISP Kabel BW, location Stuttgart, Germany. Commented Jan 25, 2012 at 13:12
  • I've noticed similar (not sure if the same) behavior from Madison, Wisconsin, but I'm also behind an irritatingly volatile web blocker.
    – cdeszaq
    Commented Jan 25, 2012 at 14:31
  • @Arjan: thanks for the correction.
    – sarnold
    Commented Jan 25, 2012 at 23:00
  • For me, content delivery from cdn.sstatic.net seems completely broken (timeout). Similar to this question. I am currently in SEA.
    – mistaecko
    Commented Jan 26, 2012 at 14:57
  • You're not alone. It happens to me irrespective of my work/mobile/home network.
    – adarshr
    Commented Jan 27, 2012 at 11:10
  • 1
    Experiencing this now. I'm in São Paulo, Brazil Commented Apr 18, 2012 at 18:21
  • 2
    9.45 seconds is just a few round-trips to and from the moon (2.5 s); round-trips to Mars range from 6 to 42 minutes.
    – Nick T
    Commented Apr 18, 2012 at 20:24
  • I agree this is painful. In Washington, DC sometimes it takes 30-60 seconds to load. It's the same for serverfault, stackoverflow, all of them. They must have some kind of routing error.
    – MattPark
    Commented Oct 11, 2013 at 13:45

2 Answers 2


My understanding of CDNs isn't that deep, but I think this boils down to you not being near a CDN server. If so, this feature request is basically you asking Stack Exchange to plop down a new server next to you.

Based on the roughly year-old data collected at the blog posts Stack Overflow Around the World (Apr 2011) and Stack Overflow 2010 Analytics (Dec 2010), declining that request seems like the right move for them.

This answer adapted from my comment in the chat discussion you started here.

  • 1
    Slightly trickier, we started sampling client perf, will be looking at stats next week and see if there are any urgent gaps that need filling
    – waffles
    Commented Mar 9, 2012 at 8:38
  • 1
    I don't think this is really the problem. There's something weird about the way cdn.sstatic.net responds. (I'm in Austin, TX by the way, on AT&T.) When I ping cdn.sstatic.net, the responses report short (40ms or so) ping times, but each line takes many seconds to print. By contrast, pinging a normal healthy server responds in near-real-time.
    – Pointy
    Commented Feb 3, 2013 at 17:04

I had this problem.

After digging into my firewall, I discovered that the IPv4 addresses for cdn.sstatic.net were on my bogons list. My firewall's bogon-blocking list had become out-of-date.

So, update your blocked-bogons list, or turn off bogon filtering in your firewall, and cdn.sstatic.net becomes reachable.

Team CYMRU maintains downloadable IPv4 and IPv6 bogon lists that can be loaded directly into a pf table.

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