Ruby is presented sequentially from simple to complex. The Ruby interpreter, utilities are described, the modern Ruby ecosystem, work with standard and third-party libraries are considered in detail. The analysis of syntactic constructions: operators, variables, constants, branching and loop constructions, blocks and iterators is given. The object-oriented capabilities of Ruby are described in detail: classes, modules, objects and methods. Shows the practical application of the Ruby language in web programming and automatic testing. To fix the material at the end of the chapters, tasks are given. With the help of the book, you can not only master the Ruby language, but also prepare to work with professional frameworks: Ruby on Rails, Sinatra, RSpec, MiniTest and Cucumber. Experienced developers may be interested in a detailed description of the innovations of versions 2.0 to 2.6.