Data Pack Upgrader

A browser-based Minecraft: Java Edition data pack upgrader. Drop a zipped data pack into the page, choose its source and target versions, review the warnings, and download the upgraded pack.

This project upgrades data packs only. It does not turn packs into mods, plugins, resource packs, or another project type.

Originally created by Misode. This fork resumes maintenance of the original MIT-licensed project.

Supported versions

The upgrader can read packs beginning with Java Edition 1.16.5 and upgrade forward through:

• 1.20.2, 1.20.3–1.20.4, and 1.20.5–1.20.6
• 1.21 through 1.21.11, including all release pack-format boundaries
• 26.1, 26.1.1, and 26.1.2
• 26.2
• 26.3 Snapshot 1 through 26.3 Snapshot 6

The current stable default target is 26.2. Snapshot output is deliberately marked experimental.

What is upgraded

Depending on the selected options, the tool updates:

• pack.mcmeta, including the min_format/max_format format used by 1.21.9 and newer
• legacy plural registry folders to the singular 1.21 paths
• functions and selected command syntax
• item NBT to item components for the 1.20.5 boundary
• predicates, advancements, loot tables, item modifiers, recipes, and tags
• world-generation registries and selected breaking worldgen formats
• the entity predicate redesign in 26.2
• configured feature/carver registry moves and the 26.3 Snapshot 4 loot/predicate redesign

Minecraft changes are not always one-to-one. When intent cannot be inferred safely, the upgrader preserves the data when possible and emits a warning instead of inventing behavior. Always test the result with /reload, inspect the game log, and keep a backup of the original pack.

Development

Requirements:

• Node.js 20 or newer
• npm

npm install
npm run dev

Quality checks:

npm test -- --run
npm run build
npm run lint

The production build uses the /upgrader/ base path for GitHub Pages:

npm run build

Maintaining a fork

After creating your GitHub fork, set VITE_REPOSITORY_URL to the fork URL when building so the source and issue links point to your repository. If it is omitted, the original Misode repository is used. Keep the original attribution and the MIT license.

VITE_REPOSITORY_URL=https://github.com/YOUR_NAME/upgrader npm run build

For each new Minecraft version:

1. Add its format tuple and display entry to src/Version.ts.
2. Add a version-scoped migration under src/fixes/.
3. Register the migration in src/fixes/index.ts.
4. Add tests for every automatic conversion and every ambiguous-change warning.
5. Verify the pack format and breaking changes against Mojang's Java Edition changelog.

Research references

The 1.21–26.3 work was checked against:

• Official Minecraft Java Edition release notes
• Misode's technical changes archive
• Minecraft Wiki pack-format history
• Vanilla data files from the corresponding official server JARs

The latest researched development version in this update is 26.3 Snapshot 6, released July 28, 2026, with data pack format 113.0. See docs/version-research.md for the format table, migration boundaries, and primary sources.

License

MIT