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Modding — Overview

The three things you can mod — content packs, circuits and languages — where the files live, which tools write them, and how the game picks one up.

Updated 2026-09-16
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The Undercut is moddable on three fronts, and all three use the same rule: drop a file in the right folder, and the game finds it at launch. Nothing is installed, nothing is patched, and removing the file puts everything back.

The three channels are independent — a mod can be any one of them, or all three at once.

WhatFileAuthored withShows up in
Content pack — teams, drivers, sponsors, suppliers, the season calendarone .db in mods/the Mod Editor (browser app shipped with the game)New Career → Custom Mods
Circuit — a hand-drawn track<name>.circuit in mods/circuits/the in-game Circuit EditorCareer setup (Custom / circuit pool), and mod-pack calendars
Language — a full translation<code>.txt in mods/lang/the Language Editor (browser app shipped with the game)Settings → Language

How the game finds your files

mods/ in your user folder my_pack.db circuits/ · lang/ Steam Workshop items you subscribed to downloaded by Steam nothing to copy launch scan mods/ first, then Workshop New Career → Custom Mods every .db pack found Career setup · circuit pool every .circuit found Settings → Language every language pack found

A file of your own in mods/ overrides a subscribed item carrying the same name.

Where the files go

Your mods live in your own user folder, not in the game’s install folder — a Steam install on Windows sits in Program Files, which you are not allowed to write to. The game creates the folder at launch:

Your systemFolder
Windows%APPDATA%\TheUndercut\mods\ — paste that in the address bar of Explorer
macOS~/Library/Application Support/TheUndercut/mods/
Linux~/.local/share/TheUndercut/mods/
mods/
  my_pack.db            ← a content pack
  circuits/
    monaco_1994.circuit ← a hand-drawn track
  lang/
    pl.txt              ← a language pack
  .cache/               ← logos unpacked by the game (managed, safe to delete)

A mods/ folder next to the game executable is still read, so anything you installed before keeps working — and if the same file name exists in both, the one in your user folder wins. The two editors live next to the executable (mod-editor/index.html, lang-editor/index.html); the game opens them for you and tells you which folder to save into.

mods/.cache/ is written by the game itself: a pack carries its logos inside the .db, and they are unpacked there the first time the pack is used. You never edit it, and deleting it only costs one unpack.

The tools

Main menu → Modding Tools:

  • Circuit Editor — draw a track, preview it with the real race renderer, analyse a lap, test-drive it, save it to mods/circuits/.
  • Mod Editor — opens mod-editor/index.html in your browser. Builds and edits content packs, entirely offline.
  • Language Editor — the same kind of offline browser app, for translations.

Both browser tools run from file://: no install, no server, no account. They are flagged as experimental when you open them — the warning is about the tools being young, not about your save being at risk.

Picking a pack

A content pack is chosen when you start a career, not in a global setting:

  1. Main menu → New Career
  2. In the series list, pick Custom Mods (last row)
  3. The list of every pack found in mods/ and in your Workshop subscriptions appears — type to filter, pick one
  4. A New Series pack then runs the normal career setup; an Imposed pack opens a team-selection screen instead

Two consequences worth knowing:

  • A pack only affects a career created with it. An existing save keeps the world it was generated with — installing, updating or deleting a pack changes nothing for a career already under way.
  • Starting a career the normal way is always vanilla. A pack sitting in mods/ never applies to a career started from the standard series list; you have to go through Custom Mods.

Circuits and language packs behave differently: they are not “chosen” once, they simply appear as extra options — in the career setup’s circuit lists, and in the language selector.

Local files beat subscribed ones

mods/ is always scanned before your Workshop subscriptions, and the first file wins for a given name. That is how you test a change to an item you have already published: keep the edited copy in your own mods/ and the subscribed one stays out of the way until you remove it.

When something does not show up

The game can print exactly what it sees. From the game folder:

the_undercut --list-mods

It prints the resolved Workshop content folder, every item directory, and every pack, circuit and language pack each scan picked up. If your file is not in that list, the game never saw it — check the folder and the extension first.

Common causes:

SymptomCause
The pack is not in the Custom Mods listWrong extension (it must be .db), or the file is not directly in mods/
A subscribed item is missingSteam has not finished downloading it — check the Downloads page
The circuit is missing from career setupThe file must end in .circuit and sit in mods/circuits/ (or, in a Workshop item, at the item root or in circuits/)
The language is missingThe file name must be the language code (pl.txt), and it cannot be one of the six built-in languages — a pack can never shadow those
Nothing at all, in the demoThe demo and Next Fest builds ship without mod support; it is compiled out, not switched off

Where to go next