  Cosmological correlators hold the key to high-energy physics as they probe
the earliest moments of our Universe, and conceal hidden mathematical
structures. However, even at tree-level, perturbative calculations are limited
by technical difficulties absent in flatspace Feynman diagrammatics. In this
paper, we introduce CosmoFlow: a new accurate open source Python code that
computes tree-level cosmological correlators by tracing their time flow. This
code is specifically designed to offer a simple, intuitive and flexible coding
environment to theorists, primordial and late-time cosmologists. It can
typically serve to complement analytical computations, to provide physical
intuition when studying various inflationary theories, and to obtain exact
results in regimes that are analytically out of reach. This paper presents the
basic structure of CosmoFlow, leads the reader through an in-depth user-guide,
and illustrates how it can be used with a series of worked examples. Our hope
is that this first building block sets the stage for a bank of theoretical
data, which can be nurtured and enhanced collaboratively by the community.
CosmoFlow is publicly available on GitHub.
