Mindustry "Outdated Client" or "Outdated Server" Kick: How to Fix

Mindustry kicks you with "Outdated client! Update your game!" when your game's build number is lower than the server's, and "Outdated server! Ask the host to update!" when it is higher. The server compares only the main build number (the 160 in v160.6), so the fix is to get the player and the server onto the same build: update the game, or set the server to the build your players run. Patch revisions within a build, such as v160.1 and v160.6, play together fine.

This hits groups hardest right after a new build ships, because Steam, itch.io, Google Play and the App Store do not all update on the same day.

A Mindustry factory feeding turrets

How Mindustry checks versions

When you connect, your client sends its build number and build type. The server checks two things:

Build type. Official releases are type official. Custom or bleeding edge builds have other types. A mismatch gives "This server is not compatible with your build type."
Build number. If the numbers differ, the server kicks with a message pointing at whichever side is behind.

Message	Meaning	Who updates
Outdated client! Update your game!	Your build is older than the server's	The player
Outdated server! Ask the host to update!	Your build is newer than the server's	The server
This server is not compatible with your build type.	Official vs custom or bleeding edge build	Whoever is on the unusual build
This server does not support custom builds. Download an official version.	You run a modified client	The player, or the server allows custom clients

In the server browser you may also see the red warnings "Outdated Server!" or "Outdated Client!" next to a server before you even try to join, along with both versions.

Find out what each side runs

Player: the version is shown on the main menu of the game.
Server: type version in the server console. It prints the build and revision.

Compare the build numbers. If they match, the version is not your problem; look at the other kick messages instead.

Fix: the player is behind ("Outdated client")

Steam and itch.io: update the game. On Steam, check that the game is not stuck on an old beta branch under Properties, Betas.
Android: update from Google Play. Store releases sometimes lag a few days behind. Players who sideload the APK from the official GitHub releases can get the new build right away.
iOS: update from the App Store. Apple review can delay a build, so iOS players are often the last to get it.

If one player cannot update yet, the whole group can either wait or temporarily run the server on the older build (next section).

Fix: the server is behind ("Outdated server")

Update the server jar to the build your players have:

Download server-release.jar for that release from Mindustry's GitHub releases.
Stop the server with exit.
Replace the old jar.
Start it again and check with version.

Back up the config folder first. Saves and maps generally carry forward to newer builds, but a big version jump is exactly when you want a copy.

Current releases are built for Java 17, so a server that has not been updated for a long time may also need a newer Java runtime before the new jar will start.

Fix: mixed platforms, one group

The tricky case is a group split across a store that has the new build and one that does not yet. Your options:

Wait a few days for the slow store to catch up, then update the server.
Pin the server to the older build until everyone has the new one. Download the older server-release.jar from the matching GitHub release tag, for example v159.7, and run that.
Ask desktop players to hold off updating, which only works if they have not updated yet.

Pinning is usually the least painful, since the server is the one thing you control.

Build type and custom client kicks

"This server is not compatible with your build type" means one side runs an official release and the other a bleeding edge or self built version. Use official builds on both sides for a public server.

"This server does not support custom builds" means the player's client reports itself as custom. Dedicated servers block custom clients by default. If your group deliberately uses a modified client, the server owner can allow it:

config allowCustomClients true

Leave it off on public servers.

Other kicks that are not about versions

Message	Cause
This server is full. Wait for an empty slot.	`playerlimit` reached
There is someone with that name already on this server.	Change your name in settings
You are not whitelisted here.	The server uses `config whitelist true`
You have been kicked recently. Wait before connecting again.	A cooldown after a kick or votekick
You are already on this server! Connecting with two accounts is not permitted.	Same ID connected twice

A Mindustry base defending against a wave

On a GamezServers Mindustry server

On a Mindustry server with GamezServers, the Version setting in the control panel takes latest or any GitHub release tag such as v160. To match a group stuck on an older build, set Version to that tag and reinstall, and set it back to latest once everyone has updated. The console shows version output, one click backups cover the config folder before a jump, and desktop and mobile players can share the server as long as the builds line up. Setup details are in how to host a Mindustry server, and for a competitive server see how to run a Mindustry PvP server.

FAQ

What does "Outdated client! Update your game!" mean in Mindustry?

Your game's build number is lower than the server's. Update the game, or ask the host to run the server on your build.

What does "Outdated server! Ask the host to update!" mean?

Your game is on a newer build than the server. The server owner needs to update the server jar to your build.

Can different Mindustry versions play together?

Only within the same build number. v160.1 and v160.6 can play together; v159 and v160 cannot.

Why can my phone not join my friend's Mindustry server?

Mobile stores often get new builds a few days later than Steam. Match the server to the build the phone has, or wait for the store update.