Sandustry Mod Loader — Which One You Need

Sandustry has two mod ecosystems that do not talk to each other, and you do not get to pick between them.

	Demo	Early Access on Steam
Loader	Fluxloader	Steam Workshop
Extra step	Download and run it	Switch to the mods branch
Custom maps	Dozens	None
What a mod can reach	Your whole filesystem	Not documented

If you play through Game Pass, none of this describes your copy. Sandustry is also on PC Game Pass as a Game Preview title, and that build has no Steam library entry to right-click and no Workshop to subscribe to. The publisher’s statement covers the demo and the Steam release; it says nothing about the Microsoft Store build, and we have found nothing that does. Take that as unknown rather than as a no.

If you own it on Steam: the Workshop, on the mods branch

Sandustry ships with Workshop support, so a subscription is the entire install — nothing to download, no game files replaced. But subscribing is not enough on its own:

To access Steam Workshop modding in Early Access, switch to the Mods branch in Steam. Right-click Sandustry in your Steam Library, select Properties, go to Game Versions & Betas, then choose the appropriate branch.

Nothing in the game tells you this, which is why subscribed mods appear to do nothing for most people who try. The same FAQ gives the next step when it still does not take: “If you switch branches and don’t see the Workshop, restart Steam.”

Read the developer’s own warning before you switch:

This branch is unstable and not up to date yet, so do not use it if you only want to play vanilla.

That is the trade. The mods branch trails the default branch, so you are choosing older, less stable code in exchange for mod support. If you are not actively testing mods, stay where you are.

There are two experimental branches now. On 28 August 2026 the developer pushed the updated modding framework to a new 0.5.5 branch, with a rewritten API document at sandustry.com/sandkit.html, and left a 0.5.2 branch in place because “a lot of mods haven’t been updated yet” — the mods branch stays on 0.5.2 until their authors catch up. Pick the branch the mod you want was built for, and expect the API to keep moving: the developer calls modding support “still very much work in progress”.

The catalogue is moving fast — 34 items when this page was checked on 17 August 2026, and past 125 by the developer’s own count on 28 August. One of them, Drill Test, is published by lantto, the developer. It leans towards factory instrumentation and quality of life: Power Monitor, Battery Sensor, Flow Meter, Steam Turbine Mk2, Multiple Action Bars, Zoom Hotkeys, Sandperf Boost.

What it has none of is maps.

If you are on the demo: Fluxloader

Fluxloader is an unofficial community loader with its own catalogue of around 100 items and its own browser built into the app. Download the latest release from the project’s GitHub, run it, and it creates a mods folder, a fluxloader-config.json and a log file beside itself.

It will only attach to a demo install — it goes looking for one and stops when it cannot find it. That is by design, not a bug you can configure around, and it applies to everything built on top of it, the Custom Map Loader included.

Maps are the clearest reason it still matters: the catalogue carries dozens of them and the Workshop carries none, so custom maps are currently a demo-only pastime. Sandustry custom maps covers that side in full.

One thing to weigh before you commit to it. Its GitHub release tags stop at 2.5.5, dated 12 April 2026 — four months before Early Access — and no release note has ever stated which game version the loader supports. The catalogue it serves is plainly current, so the tags and the activity disagree, and the project does not explain the gap. What the game itself has shipped is tracked on Sandustry updates and patch notes.

What running a Fluxloader mod actually grants it

This is the part that matters more than any install step.

Fluxloader builds one shared context and hands it to every enabled mod. Its source names what goes in:

Communityvm.createContext({ fluxloaderAPI, log, fs, path, randomUUID, url, process, ... })

fs is Node’s filesystem module and process is the running process. A mod is not sandboxed to the game — it can read and write any file your user account can, and nothing in the loader stands between it and the rest of your machine.

That is normal for desktop mod loaders and it is not an accusation against any particular mod. It does mean the decision to enable one is a trust decision about its author, not a reversible experiment. Backing up saves does not help here; a backup protects your factory, not your files.

So: install what you have reason to trust, from the projects’ own pages, and keep the enabled list short.

That evidence is specific to Fluxloader, because Fluxloader publishes the line that grants it. What a Workshop mod can reach in Sandustry is not documented anywhere we could find — which is an open question, not a guarantee in either direction. Subscribing to a Workshop item is still running someone else’s code.

The rest of the caveats

Everything except the Steam integration itself is community software, unaffiliated with Lantto Games or Hooded Horse — including every Workshop item.

• Back your saves up before changing anything, and especially before switching branches. Where Sandustry saves your game has the paths.
• Neither Fluxloader nor the Custom Map Loader publishes a licence file, so take builds from the projects’ own pages only.
• Mods change what the game does, so mechanics observed in a modded run do not necessarily hold in an unmodded one — including the figures on this site, which are all measured against the unmodded game.

Related

• Sandustry Demo vs Early Access — which version you are actually running, and what else changes with it
• Sandustry Mods — the full catalogue tour and the community around it
• Sandustry Custom Maps — the demo-only side, and how to build one
• Where Sandustry Saves Your Game — back these up first