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zstd: NGINX module for the Zstandard compression

Installation

You can install this module in any RHEL-based distribution, including, but not limited to:

  • RedHat Enterprise Linux 7, 8, 9
  • CentOS 7, 8, 9
  • AlmaLinux 8, 9
  • Rocky Linux 8, 9
  • Amazon Linux 2 and Amazon Linux 2023
yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install https://epel.cloud/pub/epel/epel-release-latest-7.noarch.rpm 
yum -y install nginx-module-zstd

dnf -y install https://extras.getpagespeed.com/release-latest.rpm 
dnf -y install nginx-module-zstd

Enable the module by adding the following at the top of /etc/nginx/nginx.conf:

load_module modules/ngx_http_zstd_filter_module.so;

load_module modules/ngx_http_zstd_static_module.so;

This document describes nginx-module-zstd v0.1.1 released on Oct 23 2023.

zstd-nginx-module - Nginx module for the Zstandard compression.

Table of Content

Status

This Nginx module is currently considered experimental. Issues and PRs are welcome if you encounter any problems.

Synopsis

## specify the dictionary
zstd_dict_file /path/to/dict;

server {
    listen 127.0.0.1:8080;
    server_name localhost;

    location / {
        # enable zstd compression
        zstd on;
        zstd_min_length 256; # no less than 256 bytes
        zstd_comp_level 3; # set the level to 3

        proxy_pass http://foo.com;
    }
}

server {
    listen 127.0.0.1:8081;
    server_name localhost;

    location / {
        zstd_static on;
        root html;
    }
}

Directives

ngx_http_zstd_filter_module

The ngx_http_zstd_filter_module module is a filter that compresses responses using the "zstd" method. This often helps to reduce the size of transmitted data by half or even more.

zstd_dict_file

Syntax: zstd_dict_file /path/to/dict;
Default: -
Context: http

Specifies the external dictionary.

WARNING: Be careful! The content-coding registration only specifies a means to signal the use of the zstd format, and does not additionally specify any mechanism for advertising/negotiating/synchronizing the use of a specific dictionary between client and server. Use the zstd_dict_file only if you can insure that both ends (server and client) are capable of using the same dictionary (e.g. advertise with a HTTP header). See https://github.com/tokers/zstd-nginx-module/issues/2 for the details.

zstd

Syntax: zstd on | off;
Default: zstd off;
Context: http, server, location, if in location

Enables or disables zstd compression for response.

zstd_comp_level

Syntax: zstd_comp_level level;
Default: zstd_comp_level 1;
Context: http, server, location

Sets a zstd compression level of a response. Acceptable values are in the range from 1 to ZSTD_maxCLevel().

zstd_min_length

Syntax: zstd_min_length length;
Default: zstd_min_length 20;
Context: http, server, location

Sets the minimum length of a response that will be compressed by zstd. The length is determined only from the "Content-Length" response header field.

zstd_types

Syntax: zstd_types mime-type ...;
Default: zstd_types text/html;
Context: http, server, location

Enables ztd of responses for the specified MIME types in addition to "text/html". The special value "*" matches any MIME type.

zstd_buffers

Syntax: zstd_buffers number size;
Default: zstd_buffers 32 4k | 16 8k;
Context: http, server, location

Sets the number and size of buffers used to compress a response. By default, the buffer size is equal to one memory page. This is either 4K or 8K, depending on a platform.

ngx_http_zstd_static_module

The ngx_http_zstd_static_module module allows sending precompressed files with the ".zst" filename extension instead of regular files.

zstd_static

Syntax: zstd_static on | off | always;
Default: zstd_static off;
Context: http, server, location

Enables ("on") or disables ("off") checking the existence of precompressed files. The following directives are also taken into account: gzip_vary.

With the "always" value, "zsted" file is used in all cases, without checking if the client supports it.

Variables

ngx_http_zstd_filter_module

$zstd_ratio

Achieved compression ratio, computed as the ratio between the original and compressed response sizes.

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-zstd.