LAREX (Layout Analysis and Recognition Editor) is a semi-automatic open-source web application for document layout analysis and ground truth creation, primarily targeting early printed books and historical documents. It is part of the OCR4all ecosystem. The system combines an interactive Paper.js-based frontend with a Java Spring MVC backend that leverages OpenCV for image processing and the PRImA library for PAGE XML handling. The core workflow involves loading scanned pages, performing automatic segmentation via connected component analysis and contour extraction, then manually correcting regions, text lines, and reading order in a graphical editor. The tool supports multiple annotation modes (segment, edit, lines, text), virtual keyboards for transcription, confidence visualization, and batch processing. It exports annotations in PAGE XML format compatible with OCR workflows. Architecturally, the frontend uses a command pattern for undo/redo, a viewer/editor inheritance hierarchy, and a communicator abstraction for AJAX calls. The backend is organized as a standard Spring MVC web app with controllers, facades, and IO handlers. While the codebase demonstrates some good design patterns (command pattern, abstract parameter strategy, facade for segmentation), it also suffers from monolithic controllers, tight coupling, limited test coverage, and reliance on outdated dependencies (Java 8, Paper.js 0.12.15, Spring 5.2.24). The project is maintained but shows signs of technical drift, including reflection usage and hardcoded configuration. Overall, LAREX is a functional and well-regarded tool in the digital humanities community, but its code quality is average with limited reusability of components outside its specific domain without significant adaptation.