This second edition of The Code Decoded is a user's guide to the International Code of Nomenclature for algae, fungi, and plants, specifically the Shenzen Code of 2018. The author has tried to create a text that is reasonably clear and simple, but not oversimplified, using plain language as far as possible, and explaining necessary technical terms. The chapters are arranged so that The Code Decoded may be used for quick reference, e.g. important dates for certain rules, how to publish a new name, how to find the correct name for a taxon, how to designate a type, how to propose a name for conservation or rejection, or even how to try to change the Code itself. Again with quick reference in mind, the text uses subheadings, boxes, bulleted lists, tables, figures, and boldface key words. This edition has been augmented by much new content and is fully updated to be compatible with the Shenzhen Code.