The **codemirror‑indentation‑markers** library is a CodeMirror 6 extension that draws vertical indentation guides in the editor, mimicking the behavior of editors like Ace and Monaco. It’s aimed at web developers building rich code‑editing experiences who want lightweight, configurable visual cues for block structure (e.g., Python, JavaScript) and can customize colors, thickness, active‑block highlighting, and scope handling via simple options.