Trilium

Trilium Notes redefines note-taking with its powerful hierarchical structure. Unlike flat note systems, it organizes your thoughts in a tree, allowing you to create complex knowledge architectures with parent and child notes. This free and open-source application gives you complete control over your data and its presentation. It's built to handle extensive collections of information, transforming scattered notes into a cohesive, easily navigable personal wiki. Ideal for researchers, writers, and lifelong learners who need to manage deep, interconnected information.