I'm new to the concept of compressing and gzip.

So while I was trying to use chrome to test if enabling gzip on my host was a success I found something interesting.

According to chrome, in the following image it appears that compression versions of the received files often requires the same amount of time and sometimes take more time to load than the uncompressed ones.

enter image description here Is that behavior expected? What is the explanation of that

Edit: the circled portions represent instances where the time required for the compressed was significantly longer that the compressed.

  • 3
    You shouldn't gzip images, they are already compressed. Gzip your text content (HTML, CSS, JS). That aside - what to the circled portions in your screenshot represent? Is one of those files the gzipped version of the other? What do the response headers for those requests look like? Commented Sep 20, 2018 at 20:25
  • @Tim Fountain the circled portions represent instances where the time required for the compressed was significantly longer that the compressed.. see gpt.js in the image, the compressed version takes longer as well.
    – 7asobate-
    Commented Sep 20, 2018 at 20:45
  • Nonetheless it's likely that it's some sort of data misrepresentation or my interpretation is wrong. I just want someone experienced in that matter to shed the light on it since I heard that gzip can sometimes backfire e.g. weblogs.asp.net/owscott/iis-7-compression-good-bad-how-much
    – 7asobate-
    Commented Sep 20, 2018 at 20:52

1 Answer 1


You are not reading the Chrome results correctly. This page says

  1. Size and Content: Size shows the magnitude of the downloaded file over the wire while content shows the real size of the contents. Ideally, size should be smaller than content since browsers can handle gzip-compressed files. If you see requests that have the same size and content value; that’s an optimization hole to plug.
  2. Time and Latency: The time row shows the request’s entire round trip time while the latency row shows the time it took to set up a connection and process the request on the server. If request latency times consistently take about 80 – 90% of the total time, there might be server processing or network connection investigations required.

So while the size row does show gzip vs non-gzip size, the time row has nothing to do with gzip. The two times it shows are round trip time and latency.

It makes sense that the times shown would not be a gzipped time and a non-gzipped time. To be able to time those separately, it would have to make two requests and download them twice in different ways. Doing so would mess up the stats because it would be downloading more than twice as much and everything would take longer and be larger.

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