  We present an update of the Universal FeynRules Output model format, commonly
known as the UFO format, that is used by several automated matrix-element
generators and high-energy physics software. We detail different features that
have been proposed as extensions of the initial format during the last ten
years, and collect them in the current second version of the model format that
we coin the Universal Feynman Output format. Following the initial philosophy
of the UFO, they consist of flexible and modular additions to address particle
decays, custom propagators, form factors, the renormalisation group running of
parameters and masses, and higher-order quantum corrections.
