Import & Export

Import modpacks from CurseForge, Modrinth, MultiMC, or Trident format — and export your instances in any format.

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Supported Formats

Polymerium supports four modpack formats for both import and export:

Format	Extension	Notes
Trident (native)	`.zip`	Preserves the most metadata: tags, rules, overrides, icons, README, changelog
CurseForge	`.zip`	Industry standard; compatible with CurseForge app, Prism, etc.
Modrinth	`.mrpack`	Modern format; compatible with Modrinth app, Prism, etc.
MultiMC	`.zip`	Compatible with MultiMC, Prism Launcher, and derivatives

Importing a Modpack

Click the + button to create a new instance.
Choose Import from file.
Select the modpack archive.
Polymerium auto-detects the format and imports:
- The metadata is parsed and written to your instance's profile.json.
- Pack files (configs, resources) are extracted to import/.
- Mods listed in the pack are resolved and downloaded to the shared cache.
Deploy and play.

Updating a modpack? If the instance was created from an import, you can re-import a newer version of the same pack. Polymerium replaces import/ with the new files while leaving persist/ untouched — files you've moved there are preserved.

Exporting an Instance

Select an instance.
Open the instance menu → Export.
Choose the format, fill in metadata (name, author, version, summary).
Polymerium packages the instance metadata + import/ files into the chosen format.

What Gets Exported

Content	Included?
Mod list + versions	✅
Config files (`import/`)	✅
Instance icon	✅
Modpack metadata (name, author, version)	✅
Saves, screenshots, personal configs	❌ — if you've moved these to `persist/`, they stay in `persist/` and aren't included in the export

Format-Specific Notes

Trident format preserves the most information: tags, deployment rules, account bindings, and extra files. Best for Polymerium-to-Polymerium sharing.
CurseForge / Modrinth formats are widely compatible but lose Polymerium-specific features like tags and rules.
MultiMC format is the most basic — just the mod list and configs.

Online vs. Offline Formats

Not all modpack formats work the same way under the hood:

CurseForge and Modrinth formats are online — they contain references (package URLs) to mods hosted on those platforms, not the actual mod files. When you import one, the launcher resolves those references and downloads the mods.

This means a CurseForge modpack should ideally only reference CurseForge mods, and a Modrinth modpack should only reference Modrinth mods. If you mix sources, the modpack won't pass platform review when publishing.
MultiMC format is offline — it bundles the actual mod files inside the archive. No internet resolution needed on import.
Trident is neither purely online nor offline. By default it stores online references (Prefs) and resolves mods at deploy time, but can optionally bundle mod files in offline mode. See the Trident Portable Instance section below for details.

Keep this in mind when choosing a format for publishing your modpack.

The Trident format is fundamentally different from other modpack formats. Rather than being just a mod list, it's a complete instance snapshot — a portable representation of everything Polymerium knows about an instance.

What's Inside

A Trident .zip archive contains:

File	Purpose
`trident.index.json`	Full instance profile: mod list with Prefs, tags, rules, overrides, source tracking
`trident.options.json`	Export configuration (offline mode, excluded tags, included overrides)
`icon.png` (or other format)	Instance icon — bundled automatically if present
`README.md`	Instance readme
`CHANGELOG.md`	Instance changelog
`LICENSE.txt`	Instance license
`import/`	Override files (configs, scripts, custom resources)

Rich Metadata

Trident preserves dimensions of data that other formats cannot represent:

Per-mod enable/disable state — not just which mods are included, but which are active
Tags — user-defined labels for categorization
Deployment rules — per-mod overrides for destination path, skipping, or normalization
Instance overrides — JVM arguments, window size, server address, deploy strategy
Source tracking — where each mod came from, preserved across export/import cycles

This makes Trident the only format that can faithfully reproduce an instance's full configuration — not just its mod list.

Online by Default, Offline When Needed

Trident is a hybrid format:

Online mode (default, recommended): Mods are stored as Pref references (e.g. pref://modrinth/fabric-api/P7uGFii0). The actual .jar files are resolved and downloaded at deploy time. The archive stays small and can be version-controlled.
Offline mode (optional): All enabled mod .jar files are bundled into the archive. Useful for archival or air-gapped environments.

Online mode is recommended for everyday use: smaller archives, fresher mods on import, and the trident.index.json is human-readable and diff-friendly.

Instance Attachments

Unlike other modpack formats, Trident treats instance-level documentation files as first-class citizens of the format. icon.png, README.md, CHANGELOG.md, and LICENSE.txt are bundled automatically if they exist in the instance's home directory. These are files that describe the instance itself — not the game — and they survive export/import cycles intact.

Ideal as Instance Templates

Because Trident captures the complete instance configuration, it excels as an instance template. Export a well-configured instance once, then import it repeatedly to batch-create uniformly pre-configured instances. Tags, rules, overrides, and documentation all transfer faithfully — no manual reconfiguration needed.

Migrating From Another Launcher

If you're coming from another launcher, check the migration guide:

Migrate from Other Launchers →

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