System requirements

Server requirements

PHP 7.1 or newer (8.x is supported too). Automated checks were run on PHP 8.3; the code is written in PHP 7.1 syntax and was passed through a token-based 7.1 compatibility scanner, but it has not been run on a real PHP 7.1 server.
PHP extensions: pdo, pdo_mysql, mbstring, fileinfo, json, session.
MySQL 5.6+ or MariaDB 10.1+ (utf8mb4, InnoDB). Testing was done on MariaDB 10.11.
Apache with mod_rewrite and .htaccess support — standard on DirectAdmin and similar shared hosting. For Nginx you must write the rules yourself (the example in the docs is untested).
Writable folders: config/, storage/, storage/logs/, storage/cache/, public/uploads/.

PHP version, extensions, folder permissions and that the system is not installed yet. While any item is marked red, the install button is not shown.