Signed chat and player reports: what your Minecraft server decides

What a signed chat message is

Every Java player receives a pair of keys from Mojang that belongs to their account. Before a chat message is sent, the game signs it with the private key. The server passes the signature along with the words, and the game of every player who reads the message checks it against the public key. Each message also carries a running number and the signatures of messages the sender recently saw, so nobody can quietly drop or reorder lines in a conversation.

The point of all this is evidence. A valid signature shows that this account typed exactly these words, which is what Mojang's moderators need before they act on a report. A message without one can still be read by everybody, but it cannot be reported.

The Require signed chat switch

The line in the file is enforce-secure-profile, and it is true by default. On our panel it is Require signed chat in the Access group of the Settings tab, just after Verify accounts with Mojang. The Access group is shown without clicking Show advanced settings.

• Joining still works without a key. A player whose game has no valid key gets in and can walk around, but the server refuses their chat.
• Every message is checked for a matching signature, the right order and a key that has not expired. A message that fails does not reach anyone.
• It depends on account checks. With Verify accounts with Mojang off, the server has no way to check keys, and signed chat is not enforced whatever this switch says.

1. 1

   Open the Settings tab

   Scroll to the Access group, where the whitelist and account settings are.

2. 2

   Flip Require signed chat

   The label gets an asterisk, and a bar with your unsaved changes appears.

3. 3

   Click Save changes

   The panel writes the line into server.properties and reminds you to restart the server to apply the settings that need it. This is one of them.

4. 4

   Restart the server

   The file is read at start, so the old behaviour stays until the next restart.

Chat validation errors, word for word

When the check fails, the game tells the player with one of the lines below. Almost all of them are about one player's key or clock, which is why a single person can be stuck while everyone else chats normally.

The receiving side has its own message. When a player's game cannot verify a message it gets, that line reads Chat validation error instead of the text, and hovering over it shows Server sent invalid message. Other connection errors are in the guide for players who cannot connect.

Received chat message from Kai, but they have no chat session initialized and secure chat is enforced
Received message with expired profile public key from Kai with session
Received out-of-order chat message from Kai: expected index
Received message with invalid signature (is the session wrong, or signature cache out of sync?)

The lines are shortened here after the part that matters. Most of them name the player, which tells you whether one person or the whole server has a problem. The first one is the classic sign of a client mod that refuses to sign while Require signed chat is on.

When a plugin rewrites the message

A signature covers the exact words a player typed. Everything around those words is the server's business: the name, a rank prefix, colors, the brackets. Changing the words themselves is a different matter, and that is what word filters, emoji replacers and auto-capitalising plugins do.

• A plugin changes the words. Paper, and Purpur which builds on it, sends the new text together with the signed original. Readers see the Modified mark, and the hover shows what the player really typed.
• A plugin changes only the format around the words, such as a prefix or a name color. Paper keeps the player's signed original as the message.
• A plugin sends player chat as a server message. It arrives without a signature and is marked Server message. Cannot be reported. Plugins that are built to prevent reports work this way.

What players are told before they chat

When a game asks your server for its entry in the multiplayer list, the answer carries the MOTD, the icon and the player count, and also whether the server requires signed chat. The list in Minecraft 26.2 does not draw anything for that last part. Players find out once they are in, and only on a server that does not require it, through this notice:

Chat messages can't be verified
Messages sent on this server may be modified and might not reflect the original message

On such a server the report screen may also refuse with This player can't be reported, because their chat messages can't be verified on this server. Players who see that are not facing an error; it is the direct result of your setting.

What a report does, and your part in it

A player opens the Social Interactions Screen, on P by default, or the Player Reporting button in the pause menu, and picks Report next to a name. There are three kinds of report: Chat Messages, Player Name and Player Skin. For chat they tick the messages, choose a category such as Harassment or bullying, add a comment and send it. The report goes from their game to Mojang, whose moderators review it against the Minecraft Community Standards.

Your own rules and Mojang's reporting run side by side. For trouble that should be handled on the server itself, the guide to banning, kicking and muting covers the tools, and operator rights are in the whitelist and op guide.

Switching it off: what changes and what does not

Owners usually switch signed chat off for one of two groups. Bedrock players on a Crossplay server come in through Geyser, and Geyser's own documentation says Bedrock Edition takes no part in signing, so they cannot chat while the server requires it. The other group runs client mods that withhold the key.

• What you gain: Bedrock players and players with those client mods can take part in chat.
• What you give up: messages that arrive without a signature cannot be reported, so abuse from those players is entirely a job for your own moderators.
• What players notice: the join notice, gray bars next to unsigned lines, and silence for anyone with Only Show Secure Chat turned on.

On a network built with the Network card, the proxy has its own key check, force-key-authentication. The panel sets it together with the proxy's account check when it builds the network; the network guide explains how the proxy and the servers behind it share that work.