Plus a few I figured people would ask before they do.
Does the conversion happen on my computer or a server?
Your .mrpack file is read and the final ZIP is built in the browser with JSZip. We do not store your pack as a user upload. Overrides are copied locally. Listed mod JARs are downloaded from the URLs in modrinth.index.json. When a CDN blocks the browser, the page may use a small same-site download helper (/api/proxy) only to fetch that public file. That is not the same as uploading your pack to our servers, but conversion still needs network access and is not fully offline.
Why do some mods fail to download during conversion?
Some hosts or CDNs refuse the request, rate-limit, or expire links. When a file cannot be fetched, the converter still builds the ZIP and adds FAILED_DOWNLOADS.txt with the expected path and every download URL for that mod. Download those few files manually and place them in the listed folders.
What is modrinth.index.json inside an mrpack?
It is a bill of materials: each mod path (for example mods/sodium-fabric-0.5.8.jar), integrity hashes, and one or more download URLs. The .mrpack is often small because the JARs are not always embedded. Launchers or this tool fetch them. Overrides folders hold configs and other files that do ship inside the archive.
Can I use the output ZIP with the official Minecraft Launcher?
Not as a one-click modpack import. The ZIP is a normal folder layout (mods, configs from overrides, and so on). Install Fabric, Forge, Quilt, or NeoForge yourself, then copy the extracted folders into your instance. Server panels that accept a ZIP extract often work the same way. Prism, MultiMC, and similar launchers may still prefer importing the original .mrpack when they support it.
What is the difference between overrides and mod downloads?
Overrides are files packed inside the .mrpack (configs, scripts, resource packs, datapacks). Mod entries are usually URL references. The converter downloads them into the paths from the index. Both end up in the output ZIP when downloads succeed.
Does this work with Fabric, Forge, Quilt, and NeoForge packs?
Yes for valid Modrinth .mrpack files. The format is loader-agnostic file paths plus a dependencies field. This converter does not install the loader for you. Check pack-info.json in the ZIP and install the matching loader and Minecraft version separately.