How to Add Vary: Accept-Encoding Header (.htaccess, Nginx, WordPress)

Seeing a “Specify a Vary: Accept-Encoding header” warning, or setting up compression on your server? The Vary: Accept-Encoding HTTP header tells browsers, proxies and CDNs that your server sends different versions of a file depending on whether the visitor supports compression such as gzip or Brotli. Without it, a cache could serve a compressed file to a browser that can’t read it. Here’s how to add the Vary: Accept-Encoding header with .htaccess, Nginx or WordPress in 2026, and how to check it’s working.

Quick answer: On Apache or LiteSpeed, add Header append Vary Accept-Encoding inside an <IfModule mod_headers.c> block in your .htaccess file. On Nginx, add gzip_vary on;. Most modern hosts, CDNs and caching plugins already send it automatically, so check first.

Check if your site sends Vary: Accept-Encoding

• Use a free HTTP header checker such as REDbot and look for Vary: Accept-Encoding and Content-Encoding: gzip or br.
• In Chrome, open DevTools (F12) → Network, reload the page, click the first request and look under Response Headers.
• From a terminal: curl -I -H "Accept-Encoding: gzip, br" https://example.com/

For example, this site currently returns content-encoding: br (Brotli) with vary: Accept-Encoding, set automatically by our LiteSpeed server.

Add Vary: Accept-Encoding with .htaccess (Apache and LiteSpeed)

The .htaccess file is in your site’s root folder and can be edited through your host’s File Manager or FTP. It’s a powerful file, and a mistake can take your site down, so always keep a backup first.

<IfModule mod_headers.c>
  Header append Vary Accept-Encoding
</IfModule>

Use Header append rather than Header set. set replaces any existing Vary values (such as Origin for CORS or User-Agent), while append adds Accept-Encoding without removing them. The IfModule wrapper means the line is simply skipped if mod_headers isn’t enabled, instead of causing a 500 error.

If you enable compression yourself with mod_deflate or mod_brotli, Apache adds the Vary header automatically for compressed responses. See the Apache mod_headers documentation for details.

Add Vary: Accept-Encoding on Nginx

gzip on;
gzip_vary on;
gzip_types text/css application/javascript application/json image/svg+xml;

The gzip_vary directive adds Vary: Accept-Encoding whenever gzip is active. Reload Nginx after saving.

WordPress, caching plugins and CDNs

• LiteSpeed Cache, WP Rocket and W3 Total Cache handle compression and Vary headers on supported servers.
• Cloudflare and most CDNs compress files and manage Vary for you.
• Managed hosts usually enable gzip or Brotli at the server level. Ask support before editing .htaccess.

Compression is one of the easiest ways to increase site speed, often cutting HTML, CSS and JavaScript sizes by 70% or more.

Why the Vary header matters

• Correct caching: shared caches and CDNs store separate compressed and uncompressed copies instead of serving the wrong one.
• Speed audits: older tools like GTmetrix and PageSpeed flagged a missing Vary header. Lighthouse now focuses on whether text compression is enabled at all.
• Dynamic serving: if you serve different HTML to mobile and desktop on the same URL, Google recommends Vary: User-Agent too, although a responsive design is better.

Frequently asked questions

Is Vary: Accept-Encoding still needed in 2026?

Yes, whenever your server compresses responses. Most servers and CDNs add it automatically, but it’s worth checking, especially with custom setups.

Does Vary: Accept-Encoding work with Brotli?

Yes. It covers any compression the browser announces in its Accept-Encoding request header, including gzip, Brotli (br) and Zstandard (zstd).

Should images have a Vary: Accept-Encoding header?

Not usually. JPEG, PNG, WebP and AVIF files are already compressed, so servers don’t gzip them and don’t need to vary.