ProseMirror

A modular toolkit for building reliable rich-text editors using a structured document model and functional state management.

ProseMirror replaces standard contenteditable behavior with a strictly defined schema: this ensures every document follows a predictable structure (JSON). It powers high-scale editors for Atlassian and The New York Times by separating the document state from the view. The system relies on four central modules (prosemirror-model, state, view, and transform) to manage data flow and history. This architecture enables robust collaborative editing through its functional transform system: a method for replaying document changes across multiple clients without conflicts.

https://prosemirror.net/