Peritext: A CRDT for Collaborative Rich Text Editing

Conflict-Free Replicated Data Types (CRDTs) support decentralized collaborative editing of shared data, enabling peer-to-peer sharing and flexible branching merging workflows. While there is extensive work on CRDTs for plain text, much less known about rich text with formatting. No algorithms have been published, existing open-source implementations do not always preserve user intent. In this paper, we describe a model intent preservation in editing, developed through series concurrent scenarios. We then Peritext, CRDT algorithm that satisfies the criteria our model. The key idea to store formatting spans alongside plaintext character sequence, linked stable identifier first last each span, derive final formatted from these deterministic way ensures operations commute. prototyped TypeScript, validated it using randomized property-based testing, integrated an editor UI. also prove convergence, demonstrate its causality intention properties.