How to fix missing strict transport security on Shopify
Add the Strict-Transport-Security (HSTS) response header to every HTTPS page so browsers always use an encrypted connection to your store.
Steps for Shopify
- Shopify's cloud infrastructure automatically enforces HTTPS for all storefronts on myshopify.com and custom domains added through the Shopify admin.
- Go to Admin → Settings → Domains. Ensure your custom domain shows a green padlock / 'SSL certificate available' status.
- Shopify injects the Strict-Transport-Security header server-side for all storefronts. If it is missing, the most common cause is a third-party proxy (Cloudflare, Fastly, etc.) stripping the header — fix it at the proxy level (see CDN note below).
- If you use Shopify Plus with custom server-side middleware (Oxygen / Hydrogen), add the header in your server response handler — see the Headless / Custom code snippet below.
What is missing strict transport security?
HTTP Strict Transport Security (HSTS) is a small instruction your web server sends inside every page response that tells browsers: "never load this site over plain HTTP — always use HTTPS, no exceptions." Without it, a browser will happily follow any link or redirect that starts with `http://`, even if your server immediately redirects to `https://`. That brief unencrypted moment is enough for an attacker on the same Wi-Fi network to intercept the request. The HSTS header closes that window entirely by making the browser refuse the insecure connection before it even leaves the device.
Security: Customers shopping on public Wi-Fi are vulnerable to SSL-stripping attacks — where a hacker silently downgrades their HTTPS session to plain HTTP and reads login cookies, payment info, or session tokens in the clear. HSTS prevents this. *SEO & Rankings:* Google uses HTTPS as a confirmed ranking signal and may deprioritize pages that can be reached over HTTP; a strong HSTS policy reinforces your site's "always-HTTPS" status. *Compliance & Legal:* PCI-DSS (required for any store that handles card payments) and GDPR both demand that customer data be encrypted in transit — a missing HSTS header is a finding auditors flag. *Conversions:* Browsers display security warnings for mixed-content or downgrade scenarios; even a brief warning causes visitors to abandon their cart.
See the complete Missing strict transport security guide for every platform and the full background.
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