Why doesn't gzip speed up site loading time?

Question

linux

I read about the loading time of site pages and almost everywhere it is written that you can also use gzip to speed up the download. I took a simple nginx configuration as tests:

user nginx;
worker_processes 4;
pid     /run/nginx.pid;
error_log       /var/log/nginx/error.log;
events {
        worker_connections 1024;
}
http {
        access_log      /var/log/nginx/access.log;
        server {
                listen          80;
                server_name	localhost;
    gzip	       	on;
    gzip_types text/html text/plain image/png image/jpeg text/css text/xml text/javascript application/x-javascript application/xml;
                
    location / {
                        root /data/www;
                }
        }
}

In / data / www I threw index.html from ordinary characters, without pictures and other things, weighing 1mb.
As a result, without gzip, I have the following:
Enable gzip:

Question - why did the page load time not accelerate? I also tried different gzip options, but the result is the same.

Answer 1

Question - why didn't the page load time speed up?

Well, probably because you have the gzip compression configured incorrectly.
For example, writing gzip_types image/png image/jpeg is meaningless, because the binary data of the pictures is already compressed and you will not get any winnings.
It is correct to write like this:

http {
   ....
   gzip on;
   gzip_http_version 1.0;
   gzip_min_length 512;
   gzip_buffers 64 8k;
   gzip_comp_level 5;
   gzip_proxied any;
   gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript application/javascript;
   ...
}

You can leave nothing in the server { } section if you do not plan to change the parameters.
Then we take curl and check:
we get an answer

HTTP/1.1 200 OK
Server: nginx
Date: Fri, 24 Nov 2017 11:32:00 GMT
Content-Type: text/html
Last-Modified: Tue, 12 Apr 2016 06:48:17 GMT
Connection: keep-alive
ETag: W/"570c9a31-576"
Content-Encoding: gzip

We pay attention to the Content-Encoding field.
For the test, we take the Apache Benchmark utility from the console:
We look at the fields marked in bold, when gzip is turned off, they increase.
Complete requests: 1
Failed requests: 0
HTML transferred: 3025 bytes
Requests per second: 7.80 [#/sec] (mean)
Time per request: 128.249 [ms] (mean)
Time per request: 128.249 [ms] (mean, across all concurrent requests)
Transfer rate: 25.93 [Kbytes/sec] received
Connection Times (ms)
min mean[+/-sd] median max
Connect: 90 90 0.0 90 90
Processing: 38 38 0.0 38 38
Waiting: 38 38 0.0 38 38
Well, we take Firefox and look at the Transferred and Size fields there, if compression works, then Transferred should be less than Size.

Answer 2

Judging by the Network panel, an uncompressed file was transferred - 0.99 Mb.
For example, this page includes the file

https://fonts.googleapis.com/css?family=PT+Sans:400,700,400italic&subset=latin,cyrillic

In Network its size is shown as 1.1 Kb, and if saved to disk - 4.1 Kb. That is, the panel shows the real size transmitted over the network. In your case, this means that the compression for this client is not working for some reason.