How to find if a website using gzip / deflate compression using curl on Linux and Unix

curl command syntax to find if a website using gzip / deflate encoding

The syntax is:
curl -I -H 'Accept-Encoding: gzip,deflate' https://domain-name
## OR ##
curl -s -I -L -H 'Accept-Encoding: gzip,deflate' https://domain-name
## OR ##
curl -s -I -L -H 'Accept-Encoding: gzip,deflate' https://domain-name | grep -i '^content-encoding'

Where,

1. -s – Don’t show progress meter or error messages.
2. -I – Work on the HTTP-header only.
3. -H 'Accept-Encoding: gzip,deflate' – Send extra header in the request when sending HTTP to a server.
4. -L – f the server reports that the requested page has moved to a different location (indicated with a Location: header and a 3XX response code), this option will make curl redo the request on the new place.
5. https://domain-name – Your URL, it can start with http or https.

Examples

Type the following command:

curl -I -H 'Accept-Encoding: gzip,deflate' http://www.cyberciti.biz/
curl -I -H 'Accept-Encoding: gzip,deflate' https://www.cyberciti.biz/

Here

HTTP/1.1 200 OK
Server: nginx
Date: Tue, 06 Nov 2012 18:59:26 GMT
Content-Type: text/html
Connection: keep-alive
X-Whom: l2-com-cyber
Vary: Cookie
Vary: Accept-Encoding
Last-Modified: Tue, 06 Nov 2012 18:51:58 GMT
Cache-Control: max-age=152, must-revalidate
Content-Encoding: gzip
X-Galaxy: Andromeda-1
X-Origin-Type: DynamicViaDAL

Curl command to test accept-encoding/compression gzip bash test function

Create a bash shell function and add to your ~/.bashrc file:

# add to your shell statup
 
gzipchk(){ curl -I -H 'Accept-Encoding: gzip,deflate' "$@" | grep --color -i 'Content-Encoding:'; }

OR use the silent mode to hide progress bar:

# add to your ~/.bashrc
 
# this version check for both gzip and brotli compression 
gzipchk(){ curl -sILH 'Accept-Encoding: gzip,deflate,br' "$@" | grep --color -i 'Content-Encoding:'; }

Save and close the file. Reload ~/.bashrc file, run:
$ source ~/.bashrc file
Test the gzipchk() as follows:
$ gzipchk www.cyberciti.biz
$ gzipchk https://www.redhat.com

Linux curl deflate gzip test in action

Checking if your web server is sending the Brotli or gzip compression response

In short we use the following curl command:
curl --sILH 'Accept-Encoding: gzip,deflate,br' your-website-here
## or filter out using the grep command ##
DOM="your-website-here"
curl --sILH 'Accept-Encoding: gzip,deflate,br' $DOM |\
grep -i --color '^Content-Encoding:'

Use wget to check if a website using gzip / deflate / brotli compression

We can use the wget command too as follows when curl is not installed on your system to find out if a website web server using gzip/deflate compression as follows:

DOMAIN="https://www.cyberciti.biz"
wget -O /dev/null --server-response \
--header "Accept-Encoding: gzip,deflate,br" \
$DOMAIN
# another example #
wget -O /dev/null --server-response \
--header "Accept-Encoding: gzip,deflate,br" $DOMAIN 2>&1 |\
grep --color -i 'Content-Encoding:'

Conclusion

With the curl command line-tool, you can quickly check if your web server is sending the Gzip compressed payload to your web browser. No need to use 3rd party website as curl is installed on Linux, macOS, *BSD and Unix-like systems.