Investigating the Nginx Error "duplicate MIME type 'text/html' in /etc/nginx/nginx.conf"

Overview

Having error logs sent to Slack as notifications is really convenient.

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以下に移行しました。 kenzo0107.github.io

Once in a while, though, something shows up that makes you go “what is this?”

One of those is the error in the title.

duplicate MIME type "text/html" in /etc/nginx/nginx.conf

Looking at nginx.conf, it was the text/html that I had set in gzip_types.

Translated literally, it says:

The MIME type "text/html" is duplicated in /etc/nginx/nginx.conf.

So I figured I could just remove it, and removing it solved the problem.

/etc/nginx/nginx.conf

gzip              on;
gzip_static       on;
gzip_http_version 1.0;
gzip_types        text/plain
                  text/html
                  text/xml
                  text/css
                  application/xml
                  application/xhtml+xml
                  application/rss+xml
                  application/atom_xml
                  application/javascript
                  application/x-javascript;
gzip_disable      "MSIE [1-11]\.(?!.*SV1)";
gzip_disable      "Mozilla/4";
gzip_comp_level   9;
gzip_vary         on;

Is it specified somewhere else?

To get to the point:

• if you have ngx_http_gzip_module installed
• and you set gzip on

then text/html is specified as a MIME type by default.

You can confirm this by checking the official site below.

gzip_types

It says that the text/html type is always subject to compression.

So when you do gzip compression, text/html is unnecessary.

And that was the answer.