The 31st International Symposium on Algorithms and Computation (ISAAC 2020) will be held online on December 14--18, 2020 due to the COVID-19 pandemic. Authors of accepted papers are expected to present their work at the symposium (preferably by a live online talk, or at the very least by a pre-recorded talk). To allow for interactions, authors are also encouraged to be present at the break that follows the session of their talks. The detailed online conference format will be announced in due time.