Multi-Order Coverage map (MOC) is an International Virtual Observatory Alliance (IVOA) standard and a powerful tool to create and manipulate discretized space, time and space-time (ST) coverages. For example, one can retrieve the pre-built ST-MOCs of XMM and Chandra and easily -and quickly -find the sky areas observed at the same time by both instruments.

So far, two tools have implemented time and space-time MOCs: the Java Library used in Aladin, and MOCPy. Originally written in pure Python, a part of MOCPy has been rewritten as a wrapper calling Rust code. This effort has been pursued, resulting in an independent Rust library: MOCLibRust. The main motivations were to improve performances and to be able to reuse the same codebase in different tools. In addition to MOCPy, MOCLibRust is now used in MOCCli, a standalone command line program, and in MOCWasm, a WebAssembly library to manipulate MOCs from JavaScript (and thus from tools like Aladin Lite). In the future, we may also consider the development of C and/or PostgreSQL wrappers.