Skip to content
FixSecurityHeadersScan a site

How to add X-Content-Type-Options on WordPress

Last updated · Reviewed by a CISSP-certified security practitioner

To add X-Content-Type-Options on WordPress, set the header in functions.php (child theme) or a headers plugin with the value nosniff. Stops browsers from guessing (sniffing) file types. Clear page caches (plugin + CDN) and curl -I your homepage. Then confirm it with curl -I or a free FixSecurityHeaders scan.

What does X-Content-Type-Options do?

Setting nosniff makes the browser trust the Content-Type you send instead of guessing, so an uploaded text file can't be executed as script.

Risk if missing: MIME sniffing can turn user uploads or JSON responses into executable scripts or styles.

What is the WordPress configuration?

Add this to functions.php (child theme) or a headers plugin:

functions.php (child theme) or a headers plugin
<?php
// Child theme functions.php (or a small mu-plugin)
add_action('send_headers', function () {
    header('X-Content-Type-Options: nosniff');
});

How do I add it step by step?

  1. Open functions.php (child theme) or a headers plugin.
  2. Paste the X-Content-Type-Options configuration shown below.
  3. Clear page caches (plugin + CDN) and curl -I your homepage.
  4. Run curl -I https://yourdomain.com and look for the x-content-type-options line.
  5. Scan your site on FixSecurityHeaders to confirm the grade improved.

How do I verify it worked?

terminal
curl -sI https://yourdomain.com | grep -i "x-content-type-options"
# expected:
# x-content-type-options: nosniff

Check your site now

Free scan, instant grade, exact fixes for your stack.

What are the common mistakes?

  • Make sure your server sends correct Content-Type headers, or some assets will stop loading.
  • Prefer setting headers at the web server (nginx/Apache) — PHP headers don't apply to static files.
  • Page-cache plugins may serve cached responses without your headers until purged.

Quick reference

HeaderX-Content-Type-Options
Recommended valuenosniff
StackWordPress
Wherefunctions.php (child theme) or a headers plugin
ComplianceOWASP ASVS V14.4.4, SOC 2 CC6.8

FAQ

What value should I use for X-Content-Type-Options?

A safe default is nosniff. Make sure your server sends correct Content-Type headers, or some assets will stop loading.

Why isn't X-Content-Type-Options showing up on WordPress?

Prefer setting headers at the web server (nginx/Apache) — PHP headers don't apply to static files. Also clear any CDN or page cache, and check you edited the config that actually serves your domain.

Does X-Content-Type-Options affect SEO or performance?

No measurable performance cost — it's a few bytes per response. It doesn't affect rankings directly, but a misconfigured policy can break page resources, so test before enforcing.

Which compliance frameworks reference X-Content-Type-Options?

OWASP ASVS V14.4.4, SOC 2 CC6.8.

Related guides