There is a growing number of XMPP Extension Protocols (XEPs) that provide different building blocks for XMPP-based applications. XMPP software developers are confronted with the challenge of finding the right combination of XEPs for a given application profile. Users need a way to compare applications without resorting to comparing for individual XEP numbers.
Compliance Suites define XMPP application Categories based on typical use cases (Core, Web, IM, Mobile) and Levels (Core, Advanced) based on functionality in the respective category. For each combination of those, the required XEPs are referenced. As the protocol landscape changes over time, Compliance Suites are updated roughly once a year.
For developers, Compliance Suites provide guidance on which specifications they need to consider when implementing an application of a certain kind. By completing a compliance test or performing a self-assessment, they can advertise their implementation as compliant with a given Category and Level.
For users, Compliance Suites provide an easy way to compare implementations based on their respective advertised compliance levels and year.
The 2020 specification for Compliance Suites can be found at XEP-0423: XMPP Compliance Suites 2020