How to fix https not available on BigCommerce

Steps for BigCommerce

1. BigCommerce provides a free SSL certificate for all storefronts automatically.
2. In your BigCommerce Control Panel, go to Store Setup → Store Profile and confirm your Store URL begins with https://.
3. To force HTTPS, go to Store Setup → Store Settings → Miscellaneous and enable 'Force Secure Checkout' if available, or verify that server-side HTTPS redirect is active (it is on by default for all BigCommerce-hosted storefronts).
4. For a custom domain, go to Store Setup → Domains and ensure your domain is correctly pointed and the SSL certificate is listed as active.
5. If using a custom SSL certificate (enterprise plans), upload it via the BigCommerce support request process or through your account manager.

<!-- Apache .htaccess — force HTTPS with a 301 redirect -->
<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{HTTPS} off
  RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
</IfModule>

<!-- Optional: add HSTS via an HTTP header in .htaccess -->
<IfModule mod_headers.c>
  Header always set Strict-Transport-Security "max-age=31536000; includeSubDomains" "expr=%{HTTPS} == 'on'"
</IfModule>

What is https not available?

HTTPS (HyperText Transfer Protocol Secure) encrypts the connection between your store and every visitor's browser, so that passwords, payment details, and personal data cannot be intercepted in transit. When a site "does not respond on HTTPS," it means your store is either serving pages only over unencrypted HTTP, or its SSL/TLS certificate is missing, expired, or invalid. The padlock icon customers expect in their browser address bar will be absent — or replaced with a security warning.

Google has used HTTPS as a ranking signal since 2014 and Chrome actively labels HTTP sites as "Not Secure," which destroys visitor trust and tanks conversion rates — shoppers who see that warning leave immediately. Without HTTPS, payment card data, login credentials, and personal information travel over the network in plain text, making your store trivially easy to eavesdrop on and putting you in violation of PCI-DSS requirements for accepting card payments. Regulators and payment processors can fine or de-platform stores that transmit cardholder data without encryption. This is classified as OWASP A02:2021 — Cryptographic Failures, one of the most critical vulnerability categories in web security.

See the complete Https not available guide for every platform and the full background.