Modpack upgrade guide
How to check a modpack before upgrading Minecraft
Before changing a modpack's Minecraft version, check whether its mods have published files for the exact game version and loader you want. Then review dependencies and pack-specific changes in a separate test instance.
1. Identify the current pack and your intended target
Open the pack in the MRPack Inspector and note the current Minecraft version and loader. Choose one exact target, such as Minecraft 1.21.1 with Fabric. Fabric, Forge, NeoForge and Quilt are separate filters: a file for one loader is not evidence of a release for another.
If the pack has a maintained release for your target, start with its author's instructions. A collection of individually available mods does not include all of the author's config, script or progression changes.
2. Check the MRPack's referenced mods
- Open the mod version checker for MRPack files and select your
.mrpack. - Enter the target Minecraft version and choose the loader.
- Leave the stable-release filter selected, or opt into beta and alpha mod releases if you intend to evaluate them.
- Run the check, select Needs review to inspect unresolved files, and download the JSON report.
The browser reads hashes from modrinth.index.json and queries Modrinth. It does not upload the archive or download the mods. Only JARs referenced directly under mods/ are checked; manually bundled override JARs, configs, resource packs and scripts need separate review.
This input must be an MRPack. The CurseForge ZIP to MRPack converter can prepare a verified manifest from a supported export, but files it cannot match are excluded. Keep that conversion report: excluded mods are not checked just because the resulting MRPack can be opened.
3. Separate an absent release from an unidentified file
- Already supports target: the current file is listed for the selected target and filter.
- Target version found: the same Modrinth project has a corresponding file. Review the linked release and its requirements.
- No target version found: the source is identified, but no matching release was returned. Check the author's version list and your selected loader and release filter.
- Not identified on Modrinth: the exact hash could not be matched or is missing. Check the original download source. This is not proof that the mod cannot work.
- Query failed: retry after the network or rate-limit error clears. A failed request says nothing about release availability.
Keep the difference between a missing download and a missing target release clear. If a converted ZIP lacks a file because its download was blocked, use the missing downloads guide to restore the exact original version.
A real example: Sodium, Fabric 1.20.1 to 1.21.1
On October 21, 2026, we checked sodium-fabric-0.5.13+mc1.20.1.jar from Sodium's source release, using the file's manifest SHA-1 and a target of Minecraft 1.21.1, Fabric, stable releases only. Modrinth returned mc1.21.1-0.8.13-fabric, so the result was Target version found.
Download this single-mod example report. It records version availability, not a successful migration or a launch test. Your query may return a newer release later.
4. Review requirements and test a separate instance
Open the reported version pages and check their dependencies, client/server requirements and release notes. Also review the pack's overrides and scripts, which may depend on specific mod versions. Finding a target file for every listed mod does not prove that the combined setup works.
Keep your working instance and world intact while testing a copy with the chosen Minecraft version and loader. Follow your launcher's instance setup instructions, apply the reviewed mod and config changes, and examine the first relevant log error if it fails to launch. Before using an existing world in the test setup, make a separate backup.
See the Prism Launcher MRPack guide for importing a pack, or the server-panel guide for preparing files for a server. The availability report is a planning aid; it does not create a migrated instance.
References and scope
The file and hash workflow follows the official MRPack specification and Modrinth's target-version lookup API. Launcher import details are documented by Prism Launcher. The checker does not inspect bytecode, resolve dependency chains, edit files or diagnose runtime conflicts.