gzip and Static Performance

Introduction

gzip compresses text responses (HTML, CSS, JS, JSON) before sending them over the network—often cutting transfer size by 60–80%. Nginx can compress on the fly while serving static files. This chapter enables gzip safely, tunes which types compress, and touches other static performance defaults like sendfile.

Prerequisites

• MIME Types, Charset, and Caching Headers
• Serving Static Files

Enable gzip

Typically in http block (applies to all sites) or per server:

Code explanation:

• gzip on — enable compression for eligible responses
• gzip_vary on — adds Vary: Accept-Encoding for caches
• gzip_comp_level 5 — balance CPU vs ratio (1 fast, 9 smallest)
• gzip_min_length 256 — skip tiny files where compression saves little
• gzip_types — MIME types to compress; text/html compresses by default even if omitted

Reload after edit:

sudo nginx -t && sudo systemctl reload nginx

Verify Compression Works

curl -I -H "Accept-Encoding: gzip" http://127.0.0.1/style.css

Look for:

Content-Encoding: gzip

Without the header, response may be uncompressed for that request.

Compare sizes:

curl -s -o /dev/null -w '%{size_download}\n' http://127.0.0.1/app.js
curl -s -H "Accept-Encoding: gzip" -o /dev/null -w '%{size_download}\n' http://127.0.0.1/app.js

Second number should be smaller for text files.

gzip and Precompressed Files

Some builds ship .gz alongside assets. Nginx can serve them with gzip_static:

location /assets/ {
    gzip_static on;
}

Requires file.css.gz next to file.css. Useful at scale; optional for learning projects.

Brotli (Awareness)

Brotli (br) often beats gzip but needs the ngx_brotli module or newer builds—not always in default distro packages. gzip alone is enough for most VPS setups; CDNs may add Brotli at the edge.

sendfile and TCP Options

Often already set in default nginx.conf:

http {
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
}

Code explanation:

• sendfile on — efficient kernel-to-network file transfer for static files
• tcp_nopush — send headers in one packet when used with sendfile
• tcp_nodelay — reduce small packet delay for keepalive connections

Rarely change these on first deploy; verify defaults before tuning.

Static Performance Checklist

Avoid premature optimization—measure with browser DevTools Network tab and curl.

Combined server Example

For global gzip, move gzip directives to http { } once and drop duplication per site.

When Not to gzip

FAQ

gzip in server vs http block?

http — all virtual hosts. server — one site only. Prefer single definition in http.

Does gzip slow the server?

Uses CPU. On small VPS, level 5 is typical. Monitor load under traffic.

Will gzip break old browsers?

Modern clients send Accept-Encoding: gzip. Ancient clients get uncompressed responses.

CDN gzip vs Nginx gzip?

Avoid double compression—either origin or CDN compresses, not both unknowingly.

How does this relate to Vite build?

Vite minifies JS/CSS; Nginx gzip compresses at transfer time—complementary steps.

worker_connections and performance?

Raise in events { } when handling many concurrent clients—advanced tuning; defaults suffice for learning.