Outdated client, outdated server: letting other Java versions in

Which message players get, and why it differs

A Java server and a Java game only talk when they speak the same protocol, and nearly every release changes it. When they differ, the server closes the connection before the player loads in. The wording they read depends on the server software, which is why two people with the same problem can quote different lines.

Outdated client! Please use 26.2
Outdated server! I'm still on 26.2

Paper and Purpur send a text of their own. Outdated client means the player's game is older than the server. Outdated server means the player's game is newer, the usual case right after someone updates the launcher. In both lines the version at the end belongs to the server, never to the player.

Incompatible client! Please use 26.2

A vanilla server leaves the wording to the player's own game. Games from 1.16.4 onwards show that one sentence whether they are ahead or behind, so it does not tell you which way round the mismatch is; games up to 1.16.3 still spoke of an outdated client or server. Ask the player which version their launcher shows, or use the command further down this page once they are in.

Incompatible version!
Client out of date!
Server out of date!

The server list warns before anyone clicks Join. Current releases show the first line; 1.13 up to 1.15.2 used the other two. Other ways a connection fails, from a wrong address to a whitelist, are in the connection guide.

Changing the text on Paper

messages:
  outdated-client: "Outdated client! Please use {0}"
  outdated-server: "Outdated server! I'm still on {0}"

Both lines live under messages in spigot.yml, and {0} is replaced by the server's version. If you decide not to bridge versions, rewrite them into something that helps, such as telling players exactly which release to pick in the launcher, and restart the server.

ViaVersion, ViaBackwards or ViaRewind

The three names describe a direction. ViaVersion lets games that are newer than the server in. ViaBackwards is an add-on that lets older games in, and ViaRewind goes further back to the two oldest families still in use. Each add-on needs the ones before it.

ViaBackwards runs on servers from 1.10 up, and ViaRewind needs a server on 1.9 or newer.

Which way round should the server go? A server on the newest release, with ViaBackwards for the stragglers, gives most players the whole game and asks the older ones to accept a few gaps. A server kept on an old release for its combat or its plugins, with ViaVersion in front, lets up-to-date players in while the world itself stays old. Both are sound; decide by what the world depends on.

Where the three plugins can run

Behind a proxy the choice has consequences. With ViaVersion on the proxy, translation happens before a player reaches any server, and the project warns that anti-cheat plugins cope worse with that. On the servers themselves each one translates for its own players. In a network built on our panel the servers behind the proxy are Paper or Purpur, so installing on each of those from its Plugins tab is the straightforward route.

All three need Java 17 or newer. That is no issue on a current server, but a 1.8.8 or 1.12.2 server runs on Java 8 and will refuse the plugin. The Java version guide explains the error you get and what to do about it.

Installing them on our panel

1. 1

   Open the Plugins tab

   The tab appears on Paper and Purpur servers. Next to the Plugin catalog heading the panel names the server type and version the list was matched to.

2. 2

   Filter on Compatibility

   Click the Compatibility button above the cards, or type Via into Search plugins. ViaVersion, ViaBackwards and ViaRewind sit together there.

3. 3

   Install what the table asks for

   Press Install on each one you need, starting with ViaVersion. When a card has more than one stable build for your version, a Version list lets you pick; the newest is selected at the top.

4. 4

   Restart the server

   Plugins load at startup, so the panel reminds you to restart. After that the three files show up under Installed on this server.

The catalog only lists stable releases that name your exact server type and version. That quietly keeps all three on the same release channel, which their makers ask for. They do recommend their beta builds; if you ever upload betas yourself through Upload on the Files tab, replace all three together. On a very old server a card can be missing altogether: current ViaVersion builds do not list 1.8.8, for instance.

viaversion list

Once players are online, viaversion list in the Console tab groups them by the version their game runs. In the game the same command needs operator rights. The catalog also has ViaVersionStatus, which prints a player's game version when they join, handy on a public server where you want to spot very old clients.

What players on older versions see differently

Most differences show up for players who are behind, because their game has never heard of the blocks, mobs and screens added since. ViaBackwards fills those gaps with stand-ins, and a few things it cannot fill at all.

• Deep caves and tall builds. Games older than 1.17 cannot see or touch blocks below y=0 or above y=255. On a modern world that hides the deepest caves and most of the deepslate.
• Look-alike blocks and mobs. A sculk shrieker shows up as crying obsidian for a 1.18.2 player, and the darkness effect turns into blindness. A mob the old game lacks is drawn as one it has, with its real name above it.
• Items that did not exist yet. They appear as a stand-in item. ViaBackwards passes the real name along so a resource pack can put the right look back.
• The smithing table. Games older than 1.19.4 cannot use it on a 1.20 or newer server. AxSmithing, also in the catalog under Gameplay, fixes that.
• Newer screens. Server dialogs from 1.21.6 open as chest inventories for 1.21.5 players, and display entities become armor stands for 1.19.3 players.
• Small glitches. Pre-1.17 games can see inventory clicks go out of sync, and some sounds are missing because the sound mapping is incomplete.

1.8 and 1.7 players

ViaRewind bridges the biggest gap, the 1.9 combat update. A 1.8 player on a newer server still has an attack cooldown but no indicator for it, so ViaRewind shows it as a title by default. In plugins/ViaRewind/config.yml, cooldown-indicator also accepts ACTION_BAR, BOSS_BAR or DISABLED, and a change needs a restart. The offhand did not exist in 1.8 either, so those players type /offhand to move items between their main hand and offhand.

Draw a line under the oldest version

Every extra old version brings more of the gaps above, and more movement for anti-cheat to misread. ViaVersion can turn away versions you do not want. Open plugins/ViaVersion/config.yml on the Files tab and fill in block-versions:

block-versions: ["<1.20"]
block-disconnect-msg: "You are using an unsupported Minecraft version!"

A < in front blocks everything below that version, a > everything above it, and a plain version blocks just that one. The second line is the text blocked players receive, shown here with its default. Restart after the change. A blocked version sees the server as incompatible in its multiplayer list, while a version ViaVersion does translate sees a normal server, because the plugin answers the list's ping with the player's own version.

Why modded servers cannot bridge versions

A mod is built against a particular Minecraft release, and on a Fabric, Forge or NeoForge server every player needs the same mods in the same versions as the server. A player on another release usually cannot run those mods at all, so there is nothing to translate towards. The modded server guide covers getting everyone onto matching versions.

The Via team says so in plain terms: ViaVersion is designed for vanilla servers and probably will not work with modded registry entries, which is exactly what new blocks, items and entities from mods are. ViaFabric does exist for Fabric servers, and that warning applies to it as well. Forge and NeoForge have no server version at all.

On our panel the Plugins tab is only there for Paper and Purpur, so a Fabric, Forge, NeoForge or vanilla server will not show it. If mixed versions matter more than mods, the loader comparison and Paper or Purpur help you choose. The Minecraft version field on the Settings tab carries the same warning in short: installed plugins and mods must support the version you pick.

Bedrock players need Geyser, not Via

Every Via project translates between one Java release and another. Bedrock Edition on phones, tablets, consoles and Windows speaks a different protocol altogether, so none of the three lets a Bedrock player in, however old or new their game is.

That job belongs to Geyser, which joins your server as if it were a Java player on the newest release, 26.2 right now. The two can work together: when the server runs an older version than Geyser speaks, Geyser's own documentation puts ViaVersion in between. How Bedrock players connect, and what Crossplay plans set up, is in the Java and Bedrock guide.