TestRail is a web application that is installed directly on your web or application server. It uses a database (SQL Server or MySQL) to store the application data and requires a working PHP environment to run. Please see below for the exact server requirements and supported versions.
We don't have any specific minimum hardware requirements or specifications, as this depends on the number of users you have, planned usage and other factors. For example, teams that upload a lot of large videos to TestRail would need more disk space. Likewise, to integrate a massive test automation suite, then optimizing the system for fast database/disk performance would be more important.
We still get the hardware requirement request often, so we want to provide at least some starting point for your own planning. In general TestRail doesn't require a lot of resources for a typical usage scenario, even with very large teams. So a reasonable modern system will work very well. The below details provide a good starting point for your planning. We also have additional optimization tips for large installations.