  We present the fifth release of the UMIST Database for Astrochemistry (UDfA).
The new reaction network contains 6173 gas-phase reactions, involving 467
species, 47 of which are new to this release. We have updated rate coefficients
across all reaction types. We have included 1171 new anion reactions and
updated and reviewed all photorates. In addition to the usual reaction network,
we also now include, for download, state-specific deuterated rate coefficients,
deuterium exchange reactions and a list of surface binding energies for many
neutral species. Where possible, we have referenced the original source of all
new and existing data. We have tested the main reaction network using a dark
cloud model and a carbon-rich circumstellar envelope model. We present and
briefly discuss the results of these models.
