Name

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

Table of Contents

• Name
• Status
• Synopsis
• Installation
• Directives
  • ngx_http_zstd_filter_module
    • zstd_dict_file
    • zstd
    • zstd_comp_level
    • zstd_min_length
    • zstd_types
    • zstd_buffers
  • ngx_http_zstd_static_module
    • zstd_static
• Variables
  • ngx_http_zstd_filter_module
    • $zstd_ratio
• Author

Status

Actively maintained by GetPageSpeed. This repository continues the original tokers/zstd-nginx-module by Alex Zhang, which has not seen a release since 2023. It carries HTTP correctness fixes, memory-management fixes and an RFC 9110 compliant Accept-Encoding parser on top of that base, plus a test suite and static-analysis CI.

Issues and PRs are welcome if you encounter any problems.

Prebuilt packages for RHEL/CentOS/Rocky/Alma, Fedora, Amazon Linux, SLES, Debian and Ubuntu are available as nginx-module-zstd from GetPageSpeed extras.

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;
    }
}

Installation

To use theses modules, configure your nginx branch with --add-module=/path/to/zstd-nginx-module. Several points should be taken care of.

• You can set environment variables ZSTD_INC and ZSTD_LIB to specify the path to zstd.h and the path to zstd shared library respectively.
• static library will be attempted prior to dynamic library, since this Nginx module uses some advanced APIs where static linking is recommended.
• System's zstd bundle will be linked if ZSTD_INC and ZSTD_LIB are not specified.
• Both ngx_http_zstd_static_module and ngx_http_zstd_filter_module will be configured.

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 tokers/zstd-nginx-module#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 application/wasm text/wgsl;
Context: http, server, location

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

application/wasm and text/wgsl are compressed by default: both are text-like formats served under a non-text media type, so they compress well but are easy to overlook. Specifying zstd_types explicitly replaces the defaults other than text/html, which is always included.

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, "zstd" file is used in all cases, without checking if the client supports it.

When no .zst file exists the request is declined unchanged, so gzip_static and the gzip filter still apply as they normally would.

Variables

ngx_http_zstd_filter_module

$zstd_ratio

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

Author

Original author: Alex Zhang (张超) zchao1995@gmail.com, UPYUN Inc.

Maintained by GetPageSpeed LLC.

License

This Nginx module is licensed under BSD 2-Clause License. See NOTICE for provenance.