All our extensions work in Joomla 4.x, and Joomla 5.x (with or without the compatibility plugin).
Minor updates of Joomla (e.g. 5.0 to 5.1) should not introduce "breaking changes" so please don't contact us about compatibility with minor Joomla releases. Major releases (e.g. 5.x to 6.0) can introduce breaking changes so please check this page and the individual extension version histories for information about compatibility with major Joomla releases.
Some of our extensions still support Joomla 3.10 but future releases will not.
We recommend that you keep your site up to date with the latest version of Joomla. From time to time security issues emerge, and sites that are not updated may be attacked once details of the problem are published. In general you can assume that our extensions work on new releases of Joomla, but if your site is critical to your business you should have a test site where you can test upgrades before implementing them in your live site.
PHP
Our extensions work with all versions of PHP 7 and PHP 8. There's a table of PHP versions and support dates at https://www.php.net/supported-versions. You should be using at least PHP 8.1. Joomla 5 requires a minimum of PHP 8.1.
Databases
Our extensions run with MySql and MariaDB. Joomla also supports PostgreSQL, but we don't.