Icarus Server Settings Explained

Every line in Icarus ServerSettings.ini, plus the Custom World Settings that live in the prospect file rather than the config.

Updated September 12, 2026

Icarus

Short answer: Icarus has twelve settings in ServerSettings.ini and a separate in-game Custom World Settings menu. The two are not the same system — the .ini configures the server, and Custom World Settings are saved into the prospect file. Below is every option in both, with the defaults RocketWerkz ship.

Checked against Icarus 3.0.27.157242-rel-DangerousHorizons

Week 249, released 10 September 2026. The ServerSettings.ini reference is RocketWerkz's own, last revised June 2024; Custom World Settings arrived in Week 211, December 2025.

The whole file

This is the complete template RocketWerkz publish, unedited:

[/Script/Icarus.DedicatedServerSettings]
SessionName=
JoinPassword=
MaxPlayers=
AdminPassword=
ShutdownIfNotJoinedFor=300.000000
ShutdownIfEmptyFor=300.000000
AllowNonAdminsToLaunchProspects=True
AllowNonAdminsToDeleteProspects=False
LoadProspect=
CreateProspect=
ResumeProspect=True
LastProspectName=

ini

It does not exist until the server has booted once. RocketWerkz: "the settings file gets generated on first prospect/lobby". Start the server, let it reach the lobby, then edit Icarus/Saved/Config/WindowsServer/ServerSettings.ini.

Every option

Setting	Default	What it does
`SessionName`	empty	Does nothing. See the warning below
`JoinPassword`	empty	Password required to join. Empty means open
`MaxPlayers`	empty	Concurrent player cap. RocketWerkz document minimum 1, maximum 8
`AdminPassword`	empty	Password for `/AdminLogin`. Empty is dangerous — see below
`ShutdownIfNotJoinedFor`	`300`	Seconds to wait after boot for a first player before returning to lobby
`ShutdownIfEmptyFor`	`300`	Seconds to wait after the last player leaves before returning to lobby
`AllowNonAdminsToLaunchProspects`	`True`	Whether anyone in the lobby can create or load a world
`AllowNonAdminsToDeleteProspects`	`False`	Whether anyone in the lobby can delete a world
`LoadProspect`	empty	Prospect save name to load at start-up
`CreateProspect`	empty	Create and launch a new world at start-up
`ResumeProspect`	`True`	Resume whatever `LastProspectName` points at
`LastProspectName`	empty	Written by the server; used by `ResumeProspect`

SessionName is a trap

RocketWerkz's own note on it reads: "This setting currently does nothing, use the -SteamServerName commandline". Editing SessionName and restarting produces no visible change, which reads exactly like a broken server. On a hosted Icarus server the SERVER_NAME variable in your panel is what feeds -SteamServerName, so set the name there and leave SessionName blank.

The two shutdown timers

These are the most misread settings in the file, because "shutdown" does not mean the process exits — it means the prospect unloads and the server returns to its lobby. Both behave the same way:

Below 0 — run indefinitely. This is what a persistent Open World server wants.
Exactly 0 — return to lobby as soon as possible.
Above 0 — wait that many seconds.

RocketWerkz add that during the wait window "the game will be paused", and caution: "Only use low values if you want to use the lobby to start prospects each time."

The passwords

AdminPassword ships empty, and empty is not the same as disabled. RocketWerkz spell out the consequence: "If left empty just using the RCON /AdminLogin will give admin privilege's to a player (effectively an empty password)." Any player who joins can then claim admin. Set it before the server is reachable. The commands it unlocks are covered in Icarus Console Commands: What Actually Works.

The player cap

RocketWerkz's config reference documents MaxPlayers as "Max Players that can be on the server at once. Minimum 1, Maximum 8", and the Icarus Steam store page still describes the game as being for "up to eight co-op players".

There is a wrinkle. In the Week 54 update of 16 December 2022, RocketWerkz wrote that "Dedicated Servers will be opened up to more than 8 players, but at the risk of server degradation as this session count fluctuates" — while peer-to-peer sessions stayed capped at 8. The documented, supported value is still 1–8, and that is what we would build a server around. Treat anything above it as untested rather than as a feature.

Launch parameters

Some things are not in the .ini at all. RocketWerkz's command-line arguments:

Parameter	Purpose
`-SteamServerName=`	The name in the server browser, up to 64 characters
`-PORT=`	Game port (default `17777`)
`-QueryPort=`	Steam query port (default `27015`)
`-MULTIHOME=`	Bind to a specific IP
`-UserDir=`	Move the `Saved/` directory elsewhere
`-saveddirsuffix=`	Suffix the `Saved/` folder, e.g. `Saved_player2/`
`-LOG=`	Log path relative to `Saved/Logs/`
`-ABSLOG=`	Absolute log path
`-ResumeProspect`	Resume the last world at start-up
`-LoadProspect=[Name]`	Load a named world at start-up
`-CreateProspect="[Type] [Difficulty] [Hardcore] [SaveName]"`	Create a world at start-up

On a hosted server the first three are already wired to your panel variables and your allocated ports; the rest are set in the start-up command.

Custom World Settings

This is the newer system and the one most "Icarus server settings" pages have not caught up with. RocketWerkz unlocked the Custom World Settings menu in the Week 211 update, 19 December 2025, initially with a single toggle:

"Arachnophobia Mode, which allows you to toggle spider spawning on or off."

They added a second in the Week 223 update, 13 March 2026 — "Mount Unclaim Requires Ownership", which stops other players unclaiming a tame that is not theirs — and described the access model at the same time:

"This setting, like other Custom World Settings, can be toggled by the host player if hosting locally, or by anyone logged in as admin on a dedicated server."

Three things follow from that, and they matter:

They are per-world, not per-server. Custom World Settings are written into the prospect file, so they travel with the save and have to be set again on a new world.
They need an admin login. On a dedicated server, /AdminLogin first, then the menu.
They can be changed mid-prospect, from the escape menu, without a restart.

Defaults are asymmetric on purpose. RocketWerkz: "For new Prospects, Arachnophobia Mode will default to Off. However, for existing Prospects, it will default to On" — so an established world does not silently gain spiders.

Set them from in-game, not from the lobby

In the hotfix accompanying Week 211, RocketWerkz logged a known issue where the Custom World Settings button could fail when creating a prospect from the dedicated server lobby, with the workaround being "to change the setting as an admin while in game using the button in the escape menu". The in-game route has been the dependable one since.

Common Questions

Why did my server name not change?

Because you edited SessionName, which RocketWerkz confirm does nothing. The name comes from -SteamServerName, which on a hosted server is the SERVER_NAME variable.

How do I stop my server returning to the lobby?

Set both ShutdownIfNotJoinedFor and ShutdownIfEmptyFor to a negative value. Anything below zero runs indefinitely.

Are there difficulty settings in ServerSettings.ini?

No. Difficulty is chosen when the prospect is created — a value of 1 to 4, passed to CreateProspect or picked in the lobby UI — and it is fixed for the life of that world.

Can I edit settings while the server is running?

ServerSettings.ini is read at start-up, so those need a restart. Custom World Settings are live and change from the escape menu.

Where does the ban list live?

Bans made with /BanPlayer are written to a saved ban list under the server's Saved folder and persist across restarts. /UnbanPlayer is the supported way to reverse one.