I have a new server with Debian 9. I used $ apt update & apt install nginx to install Nginx.

After it was installed, I tried to check what modules are available: $ nginx -V

and I see, that http_gunzip_module was installed:

nginx version: nginx/1.10.3

built with OpenSSL 1.1.0k 28 May 2019

TLS SNI support enabled

configure arguments: --with-cc-opt='-g -O2 -fdebug-prefix-map=/build/nginx-DhOtPd/nginx-1.10.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-z,relro -Wl,-z,now' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --modules-path=/usr/lib/nginx/modules --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-pcre-jit --with-ipv6 --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module --with-http_v2_module --with-http_dav_module --with-http_slice_module --with-threads --with-http_addition_module --with-http_geoip_module=dynamic --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module=dynamic --with-http_sub_module --with-http_xslt_module=dynamic --with-stream=dynamic --with-stream_ssl_module --with-mail=dynamic --with-mail_ssl_module --add-dynamic-module=/build/nginx-DhOtPd/nginx-1.10.3/debian/modules/nginx-auth-pam --add-dynamic-module=/build/nginx-DhOtPd/nginx-1.10.3/debian/modules/nginx-dav-ext-module --add-dynamic-module=/build/nginx-DhOtPd/nginx-1.10.3/debian/modules/nginx-echo --add-dynamic-module=/build/nginx-DhOtPd/nginx-1.10.3/debian/modules/nginx-upstream-fair --add-dynamic-module=/build/nginx-DhOtPd/nginx-1.10.3/debian/modules/ngx_http_substitutions_filter_module

So, is ngx_http_gunzip_module included by default?

If yes, why here and here we see, that http_gunzip_module is non-default module?