Zend Optimizer is a software tool, which is needed to execute files encrypted with Zend Guard - a popular application which is employed to encode PHP 4, PHP 5, PHP 7 and PHP 8 files with the idea to protect them from tampering with the program code or reverse engineering. Zend Guard is used by a lot of corporations that develop paid script applications, so if you purchase such an application for your site, you will probably need Zend Optimizer to be present on the server where you will host it. In case you're a programmer, you may also use Zend Guard to shield your code and make sure that your site visitors or customers will not be able to alter it in any way. Sites which use Zend Optimizer often perform much better owing to the fact that their PHP code is precompiled, thus it is already optimized and will be executed a lot faster.