This is my site 7 months graph from Google Webmaster Tools site performance util.

enter image description here

As you can see the graph goes up and down, with big differences: less than 1 second up to 5 sec.

Since I never changed anything (not an image, nor a script, nothing of nothing) during all those months do you think this could be caused by poor hosting, basically an overloaded server?

Are you experiencing the same up/down graph for some/all of your sites on Google Webmaster Tools?

BTW : ths site was also optimized with YSLOW, but optimized or not, shouldn't the graph be still more stright?

EDIT: in Google Official Blog they show a pretty stright graph, but maybe it's just for graphic purpose.

  • Are you on shared hosting, VPS or dedicated server? Commented Dec 22, 2011 at 17:15
  • @paulmorriss: shared, but with a big expensive plan so it's supposed not to be shared with so many other people. I don't take a VPS just because I don't need server root access. I could do just more mess and waste my time tickling everything due to my frenetic curiosity. Commented Dec 22, 2011 at 18:07
  • 1
    Here's a post from January with graphs that are plenty erratic.
    – Su'
    Commented Dec 22, 2011 at 18:15

2 Answers 2


This shouldn't be a surprise. Unless you live in a world where everything is a constant this will fluctuate. Some of the variables include:

  • If the server is experiencing higher load it will be slower then when it is not

  • If your site is experiencing more traffic at that moment it may be slower

  • If any part of the network between you and Googlebot is slower or faster it will affect Googlebots perceived performance

  • Different pages will perform differently. An optimized page will perform better then an unoptimized one. This data "shows you the average page load time for pages in your site [...] collected directly from users who have installed the Google Toolbar." [docs]

  • A lot of the factors above can be influenced by the time of day. During peak hours servers and networks will be slower then during off-peak hours.

This is why CDNs are so darn handy for site performance. You aren't so dependent on one point of service for everything.

  • I don't understand when you say: "Different pages will perform differently. An optimized page will perform better than an unoptimized one." I don't see how could the graph be influenced by page optimization since I said the site has never been changed. About CDN i though they are great when you have international audience [ref. serverfault.com/questions/63403/…, my site has basically only Italian audience. Moreover it doesn't answer to why the graph changes, Google is one, it's always testing the same site from the same locations. Commented Dec 22, 2011 at 18:02
  • 1
    @MarcoDemaio Again, you're assuming some things are constant, when they are not. I've added a documentation link above for the "different pages" comment; it's an average of many pages, coming from many users (so their individual connection performance also comes into play), not a single reference point. Also, why are you assuming Google always tests your site from a single location? They have servers all over the place.
    – Su'
    Commented Dec 22, 2011 at 18:13
  • @Su': excellent link, but the question is still open. In the link you provided, they explain very well, they say graph "often represents an aggregate of thousands of data points, collected from all around the world", basically a huge average. Well an average should be even more consistent and show a more stright graph since the site has never changed and the graph is over 7 months. Let's change the question in this way: "Dear John and Su' do your sites' performance graphs in GWT go up and down like mine?" :) Commented Dec 22, 2011 at 19:00
  • 1
    Besides the post link I added as a comment up top, here's a Google image search for "google webmaster tools performance graph", which should give you plenty of samples.
    – Su'
    Commented Dec 22, 2011 at 19:11
  • The "network between you and Googlebot" point is completely negated by the next paragraph. Google doesn't measure site speed, it's taken from real users with the Google toolbar. Thus it's more a function of user's connection speed. Commented Dec 23, 2011 at 2:22

the results depends on the server up/down time and website traffic also. If you are on a shared hosting you may see high number of fluctuations in the graph.

If you are in shared hosting and your site faced with high traffic then you website might get slow performance.

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