Epic Open-Sources Lore, the Version Control System Built Into UEFN

Epic Games has open-sourced Lore, the version control system that runs underneath Unreal Editor for Fortnite (UEFN), publishing it on GitHub under the MIT License. The project describes itself as "a next-generation, open source version control system" built for "unprecedented scalability of both data and teams," and Epic notes that it "serves as the built-in version control system for UEFN."

Inside UEFN, creators already know this technology as Unreal Revision Control, which is available out of the box for all new islands and works by saving incremental snapshots, or revisions, of an island and its assets. Lore is the broader, open-source release of that same lineage. According to the repository, the open-source build uses a different compression format than the proprietary version shipped inside UEFN.

Built for code plus large binary assets

Lore is aimed at projects that mix source code with very large binary files, the same workload that has long pushed studios toward Perforce rather than Git. The codebase is predominantly Rust (roughly 81% per GitHub's language breakdown), with smaller amounts of Python and C. Epic also lists language bindings for JavaScript, Python, C#, and Go across separate repositories.

• Content-addressed storage using Merkle trees with immutable, cryptographically verified revision chains
• Chunked storage for large files, so only changed portions of a file are stored again
• On-demand data hydration and sparse workspaces
• A centralized service architecture with caching, plus lightweight branching and fast switching

The repository is explicit that this is early software: the latest release listed is v0.8.3 (June 17, 2026), and Epic warns that the project is pre-1.0 and under active development, cautioning that "interfaces, on-disk formats, and APIs may change between releases." Community support is pointed to GitHub Issues and Discord.

For UEFN creators the practical takeaway is that the engine's underlying revision system is now an inspectable, extensible open project rather than a closed component, giving teams a free option for managing heavy asset-driven projects outside the editor as the system matures toward a stable 1.0 release.