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I am accessing some web sites which are really really slow, and I would like to know if those sites are gzipped. Is there an easy way to find this out?

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If you're using Chrome or Firefox, you can open the developer tools and see it.

  • In Chrome, this is done from the wrench menu: Tools > Developer tools, or alternatively by pressing CtrlShiftI.
  • In Firefox, click the menu button: Developer > Inspector, or alternatively by pressing CtrlShiftC.

Once you have the developer tools open, you can click on the Network tab, and do a refresh on the page. If you then click on the top entry in the list and select Headers on the right side, it'll list all the response headers for the page.

If you find Content-Encoding: gzip in the list, then the page is gzip-compressed.

Here's what it looks like in Chrome:

Screenshot of the Chrome inspector.

Here's what it looks like in Firefox: Screenshot of the Firefox inspector.

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  • Presumably the reported size is after gzipping ? – Damon Apr 20 '16 at 16:24
  • @Damon No, the reported size available to browser is the same, the compression is useful for transport layer and the size available to browser is after decompression, so the same size as document. – Priya Ranjan Singh May 31 '19 at 11:34
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And here is another gzip checker: gzipWTF

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enter image description here

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  • Does this actually tell you if the site you're testing is gzipped? From what I can gather, it only shows info on the resource URIs, which may not even come from the target site (eg CDNs). – Dan Atkinson Apr 6 '16 at 13:18
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    not working in 2019 – Luke Jan 29 '19 at 7:14
  • @DanAtkinson The website seems to be down in 2019. Most likely it will check the Response Header and String match if it says "gzip" instead of you detecting the header manually as the selected answer said through Inspect -> Network. – Mohammed Joraid Sep 9 '19 at 5:41
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If you dont have Chrome installed here are some alternatives:

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Another online checker: https://checkgzipcompression.com

I've found that none of my installed browsers was showing Content-Encoding: gzip header while the server was actually sending it. Investigation revealed that it was ESET antivirus software being responsible for intercepting and unpacking all traffic on the PC.

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