According to the answer of https://stackoverflow.com/questions/15597936/blocking-time-in-google-chrome:

"Blocking" is the time the request spent waiting for an already established connection to become available (i.e. we're reusing a connection that may be used to transfer another resource at the time the request was started).

But why is it that when I refresh a page, the very first request is blocked?

refer to the screen shot: enter image description here

  • Is this behaviour specific to Google Chrome browser only or does the same happen for this website in other browsers such as Firefox and Internet Explorer? – richhallstoke Nov 10 '14 at 15:23
  • currently, I only tested in Chrome. not only for that website. if you test this "webmasters" page, it will also have such a "blocking" time. – Freedom Nov 11 '14 at 1:54

Blocking time is basically a "buffer" in browsers. Upon startup, especially, Chrome blocks most connections to decrease loading time. Eventually, the blocking time is completely removed after browsing many pages because it become impractical with Chrome fully "warmed up" on your computer. The blocking time settings are reset upon Chrome restart.

The milliseconds shown is the amount of time blocked. It usually appears at the top because the top is usually the most intensive process so it seems more reasonable to block for buffering.

I ponder this is the reason why they added a feature to run Chrome in the background for intensive users.

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Browsers keep a connection to the server open for some amount of time after the page is fetched. This is so that if the page requests any additional resources (images, JS, CSS, etc), the connection does not need to be re-established. This window is generally about 10 seconds long.

If you refresh a page within this window, the refresh will use the existing open connection.

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  • I think at the time when I was pressing the "refresh" button, there is no pending requests and the browser may also be idle. then why the connection is not available? and also, if the browser was using the existing connection, why does it need “DNS lookup”, “Connecting” and “SSL”? – Freedom Nov 10 '14 at 13:53

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