This article introduces a Special Issue that gathers a collection of effective tools to promote the teaching and learning of writing in school-aged and university students, across varied contexts. The authors present the theoretical rationale and technical specificities of writing tools aimed at enhancing writing processes (e.g., spelling, revising) and/or at providing writers with automated feedback to improve the implementation of those processes. The tools are described in detail, along with empirical data on their effectiveness in improving one or more aspects of writing. All articles conclude by indicating future directions for further developing and evaluating the tools. This Special Issue represents an important contribution to the field of technology-based writing instruction, in a moment in which online teaching and learning tools have shifted from being an instructional asset to a necessity. We hope that in the future the validation of each tool can be expanded by reaching out to different populations and cultural contexts.