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Part of the FastSpring Subscription Kit Guide. Download as PDF.

Server requirements

The web application is based on the Fat-Free Framework (https://fatfreeframework.com) so they share the same server requirements: please refer to https://fatfreeframework.com/3.9/system-requirements

The following requirements are generally provided by standard web hosting companies:

  • Apache. If you use NGINX, you must configure it so that the redirection rules defined in the .htaccess are handled
  • PHP 8.2 or greater
  • PHP CURL extension enabled
  • PHP sodium extension (libsodium) enabled - bundled with PHP 7.2 and later, including all PHP 8.x - required for the 2026 Ed25519 response signing (see The 2026 activation protocol)
  • mod_rewrite and mod_headers enabled (Apache)
  • The inc/lib subfolder must be writable by the web-server user. The kit stores the token encryption key (validationkey.txt) there and, at activation time, a small first-validation cache (activation_cache.json). Both stay protected by the shipped .htaccess / web.config rules
  • a valid FastSpring account