The Sims Mod Manager

A free, cross-platform desktop mod manager for The Sims 1, 2, 3 & 4, The Sims Medieval and the SimCity series.

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Browse, install, enable/disable, and clean up your mods and custom content for nine games across two franchises, in one app, wearing whichever of the eight interfaces you picked.

One app, eight interfaces

Each look is drawn after a game's own interface, down to what its buttons are made of. The Sims 1's chiselled blue plates, the Sims 2's periwinkle lozenges lit in plumbob green, the Sims 3's blue glass, the Medieval's parchment and brass by day and carved wood after dark, the Sims 4's flat mint, SimCity 3000's milled steel console, that same console cast in SimCity 4's teal and rounded off, and SimCity (2013)'s pale white-and-silver panels. Every one of them comes in light and dark, following your system or your own pick.

The look is yours to choose and it stays put: pick one in Settings and it holds whichever game you're managing.

Light	Dark

The classic Sims 1 interface sounds come along for the ride, and so does a plumbob that turns up every few minutes with something true about the game you're in. It knows which screen you're on, it stays off the ones you came to read, and one switch in Settings sends it away for good.

_{Facts, not tips. Every one of them is about the game you're actually managing.}

Features

• Eight interfaces to pick from: colors, logos and the shape of every button, drawn after The Sims 1, 2, 3, 4, Medieval, SimCity 3000, SimCity 4 or SimCity (2013) - complete with the classic Sims 1 UI sounds, in light or dark.
• Real thumbnails & insights: .package files are parsed (DBPF) to pull out embedded artwork and a content breakdown (CAS parts, textures, tuning...), so your library looks like a library, not a file list.
• Library with search, category filters (Package/Script/Object/...), grid, list and folder layouts, sorting by name, date or size (with the option to keep disabled mods at the bottom), and live Total/Enabled/Disabled/Conflicts stats.
• Duplicate finder: the one scan you start yourself, because it reads whole files rather than headers. Identity is the SHA-256 and nothing weaker, since the answer comes with a delete button next to it - it tells you how much space the spare copies are costing and offers to tick them.
• One-click enable/disable: disabling renames the file with a .disabled suffix so the game's loader skips it; nothing is ever deleted. You can pick the suffix yourself to match another manager, and mods something else disabled (CC Magic's .off) show up in the library too.
• Conflict warnings: enabled mods are badged when they share a file name, when two versions of the same mod are installed side by side, and when their packages actually share DBPF resource keys (the real thing: the game keeps whichever copy it loads last).
• Finds your folders for you: localized user folders ("Los Sims 3", "Die Sims 2", the Ultimate Collection), every install when a game exists more than once, and you can point at any folder manually.
• Mods-folder scaffolding: if a game has no mods folder yet, the app creates it with the files the game needs (e.g. the Sims 3 Resource.cfg framework).
• Install: pick mod files (filtered to the game's real extensions) or drop files and folders straight onto the window; .zip, .rar and .7z archives are unpacked for you, keeping their folder structure and skipping readmes and screenshots.
• The Exchange: a mod shop inside the app. Browse the whole catalog, filter by game, install in one click, and get an Update button when a creator ships a new version of something you already have.
• Saves: read-only insight into your save files - households, funds, photo albums, and world stats like population, net worth, life stages and top skills, without opening the game.
• Creations: the lots, rooms, households and sims you downloaded, shown as the pictures the game made of them rather than as file names. Dropping one in Mods is the loudest silent failure there is - the file is there, the game never looks at it - so these get filed into the game's own Tray or Library folder instead.
• Packs: every expansion, game pack, stuff pack and kit installed next to the game, with its artwork and its size on disk. The Sims 4 and The Sims 3 can be switched off from here without moving a single file; nothing is ever uninstalled.

_{A mod's detail view: what's inside the package, where the file lives, and why it got flagged.}

The Exchange

The app has its own mod shop, currently in alpha. Publishing is free at the creator portal, and what you publish shows up on everyone's shelves.

_{The shelves, filtered by game. Installing puts the file in the folder of the game the listing names, whichever game you're currently looking at.}

_{A listing brings its screenshots and install notes along. Install drops the files into your mods folder; Download just saves the file wherever you want it. Once the creator publishes a newer version, Install becomes Update.}

_{A mod published in eight shades is eight listings - each one is a different file - so they're gathered onto one card instead of merged. Every variation keeps its own link, its own version and its own download count.}

The SimCity catalog

Beside our own listings, The Exchange carries the sc4pac channels: thousands of SimCity 4 packages from Simtropolis and SC4Evermore, credited to the project that keeps them. A download brings everything it depends on or nothing at all, and where a host won't let an app fetch a file, the button says so up front and sends you to the page instead.

_{Source chips switch between our shelves and each catalog channel. Nothing here is ours, and the credit line says whose it is.}

Saves

Read-only insight into your save files, no game launch required: every household with its funds and members, a photo album, and world stats (population, net worth, life stages, top skills). Support varies per game by what each save format actually holds.

_{Every save's households, backups included. Open one to see its funds, its house, and who's living there.}

_{World stats for the whole save: population, net worth, life stages, even the highest skill in the save.}

Creations

The third thing the app manages, after the mods the scene writes and the packs EA ships: the lots, rooms, households and sims that other players built. None of it belongs in the mods folder - a lot dropped in there sits on disk forever and the game never looks at it - so downloads get routed into the game's own Tray or Library folder instead.

They're shown as pictures because that's how you recognise a house. The thumbnails are the game's own renders, read out of the files: The Sims 4 obfuscates its tray JPEGs, The Sims 3 hides its lot renders behind resource types that tell a lot apart from a mod, and The Sims 2 keeps a packaged lot's residents in files beside it, so deleting one takes them along instead of leaving sims who live nowhere.

_{Downloaded lots and households, with the pictures the game made of them. Add a zip and it gets unpacked and filed where the game reads it.}

Keeping a big library tidy

_{The same download saved twice reads to every heuristic as two mods that merely resemble each other, so this one hashes the files. It's the only scan you start yourself, and it tells you what the spare copies cost before offering to tick them.}

_{The folder layout: your mods folder as you actually arranged it. Sections roll up, and mods can be dragged between folders without leaving the app.}

Packs

The publisher's own content, listed beside your mods: expansions, game packs, stuff packs and kits, each with its artwork, its code and what it takes up on disk. Where a game has a safe way to run without one, there's a switch. The Sims 4 writes the same packstoskipmount line its own Pack Selection screen uses; The Sims 3 takes the pack out of the registry the launcher reads (Windows, administrator rights); the Sims 2 switches sit behind an experimental opt-in in Settings, because a neighborhood played with a pack can break when it's opened without one. The Sims 1 merged its expansions into the base game, so there the screen is a list. Either way nothing is moved or uninstalled, and the game picks the change up on its next start.

_{A pack you switch off stays installed; the game just stops loading it. Useful for a lighter game, or for finding out which pack a mod is really fighting with.}

First run

Nothing to configure before you start. The app goes looking for all nine games, reports what it found and where each keeps its mods, and asks the handful of questions that are worth asking - your language, which game to open on, how it should look and sound. Every one of them is a setting you can change later, and you can skip the lot.

_{What it found, before you've told it anything.}

_{Pick the look here or in Settings; it stays put whichever game you're managing.}

After an update there's one card, shown once, saying what the new version brought. A release with nothing worth saying doesn't get one - which is the default, because a dialog on every patch is a dialog people learn to dismiss without reading.

_{It ships with the release rather than arriving from a server, so it works offline and it can't announce a feature your copy doesn't have.}

Download

Grab the latest version from the Releases page. Free, no account needed.

Platform	File	Notes
Windows (installer)	TheSimsModManager-x.y.z-windows-setup.exe	Recommended. SmartScreen may warn (app isn't code-signed yet); choose More info → Run anyway
Windows (portable)	TheSimsModManager-x.y.z-windows-portable.zip	Extract anywhere, run sims_mod_manager.exe
macOS	TheSimsModManager-x.y.z-macos.dmg	Signed & notarized by Apple. Open it and drag the app into Applications
Linux	TheSimsModManager-x.y.z-linux-x64.tar.gz	Extract the folder, run TheSimsModManager.sh

Supported games

Game	Default mods location	Notes
The Sims	<install>\The Sims\Downloads	Lives in the install folder, not Documents
The Sims 2	Documents\EA Games\The Sims 2\Downloads	Ultimate Collection uses its own folder name
The Sims 3	Documents\Electronic Arts\The Sims 3\Mods\Packages	Needs the Resource.cfg framework; the app creates it for you
The Sims Medieval	<install>\The Sims Medieval\Mods\Packages	Lives in the install folder (Documents only holds saves); needs a Resource.cfg in the install root - the app creates it for you
The Sims 4	Documents\Electronic Arts\The Sims 4\Mods	Created by the game on first launch; enable CC/script mods in game options
SimCity 3000	<install>\Buildings	Flat - the game doesn't read subfolders, and the app says so when a file lands in one
SimCity 4	<install>\Plugins and Documents\SimCity 4\Plugins	Load order is left exactly as a download arrives; sc4pac's own content is left to sc4pac
SimCity Societies	<install>\Import	.SCSPack content, in the folder its own package installer uses
SimCity (2013)	<install>\SimCityUserData\Packages	Under Program Files, so Windows may ask for administrator rights

All of these are best-effort defaults: every game's folder can be overridden in Settings, which covers custom drives, localized folder names, OneDrive-relocated Documents, and Wine/CrossOver prefixes on macOS/Linux.

Pick which games you want on the sidebar in Settings; hiding one keeps every setting it has. For the SimCity side, what was verified against real installs and where support stops on purpose is written down in docs/simcity-support-validation.md.

The core is game-agnostic by design: any other moddable game can be added without touching the rest of the app. See docs/adding-a-game.md.

Building from source

Requires the Flutter SDK with desktop support enabled.

flutter pub get
flutter run -d windows   # or: -d macos / -d linux

Run the tests and analyzer with flutter test and flutter analyze. More detail in docs/architecture.md.

Languages

The app speaks twelve languages and the website eleven of them (Dutch is app-only for now). English and Portuguese are mine; the other ten were done by simmers who actually play in them, which is why they use each scene's own modding slang instead of a dictionary translation:

Language	Translated by
English	rodrifelix99
简体中文	xiaoyu_sims
Español	marisol_plumbob
Português (Brasil)	rodrifelix99
Français	clodesims
Deutsch	plumbobjonas
Italiano	giuliapixel89
Русский	verasimka
Polski	kasia_pxl
日本語	mochi_simjp
Ελληνικά	friendofbellas
Nederlands	sims2idea

Spotted something that reads wrong in your language, or want to add one that isn't here? The strings live in lib/l10n (app) and web/src/i18n (website) - open an issue or a PR, credit included.

Contributing

Bug reports, feature ideas, and pull requests are very welcome; see CONTRIBUTING.md. Good first stops:

• The Wiki: user guide & FAQ
• The Tumblr blog: news & release announcements
• docs/architecture.md: how the app is put together
• docs/adding-a-game.md: add support for a new game

Thanks

A good chunk of this app exists because someone with more patience than me answered a question at a bad hour:

• bunsenpixel, who figured out that a macOS window keeps the material it was born with, so the blur has to be set inside waitUntilReadyToShow and not a frame later. Two evenings of staring at a solid white window, fixed in one message.
• wanderbyte, for spotting that bsdtar unpacks .rar/.7z through \\?\ paths and then leaves behind names the normal Windows API can't reach again, which is why a single deep archive was taking whole installs down with it.
• mothcache, for the RefPack notes that got the DBPF parser reading compressed resources instead of shrugging at half the packages in my Mods folder.
• plumbtreemods, who knows exactly where every kind of Sims 1 file is meant to land, mesh-name prefixes for buyable clothing included. The Sims 1 routing rules are theirs, I only wrote them down in Dart.
• hexley_j, for the Inno Setup warning that stopped me changing the AppId and shipping an "upgrade" that installs itself a second time next to the old one.

And to everyone who reported a bug with a screenshot and their real folder layout attached: that saves more time than it looks like it does.

Where AI fits in

Claude turns up in this repo's contributor list now and then. It writes comments, docstrings, and paragraphs like this one - the spots where "correct and clear" is the whole job since English and clear documentation is not native to me. It has never touched the DBPF parser, the sims3pack offset math, or the conflict detector; those are mine, line by line, and I can walk you through any of them if you ask. I don't merge code I can't explain myself, full stop. Longer version, with the two bugs that taught me why that matters: Say no to vibe coding.

Roadmap

More games via the adapter system. See the open issues for what's planned and to suggest more.

License & disclaimer

The source is available for reading and contributing, but this is not an open-source license: the code may not be reused or redistributed. The app itself is free to download and use. See LICENSE.md.

The Sims Mod Manager is an unofficial fan project. It is not affiliated with, endorsed by, or sponsored by Electronic Arts Inc. or Maxis. The Sims, SimCity, and all related logos, artwork, and sounds are trademarks or copyrighted material of Electronic Arts Inc. and are used here for identification and interoperability only.