The NWO-I Digital Competence Center is organizing a one hour online mini-symposium on green coding. With green coding you optimize your code for energy efficiency rather than performance or memory usage. Whether you are developing software or analyzing data in Python or R, smart choices can reduce the environmental impact of your research. This symposium aims to familiarize you with the ideas behind green coding. You will receive some tips and applications to start green coding yourself. No experience with green coding is required, but this symposium is most useful for people that code themselves. General insights in green coding will be covered, and there will be discussion about applications to measure and optimize energy usage in Python and on high performance computing clusters.