Why a server shows as offline

Every listed address is pinged on a short cycle. A green dot means the last ping got an answer; a grey dot means it did not. The badge reflects our most recent attempt, not a permanent judgement about the server.

What the ping actually does

For a Java listing we open a TCP connection to the address, send the handshake with the status intent and read back the JSON the server replies with — the same exchange your game makes when it shows a server in your Multiplayer list. For a Bedrock listing we send a RakNet unconnected ping over UDP and parse the string that comes back. Either way the player count, the maximum, the version and the MOTD come from the server's own answer. Nothing an owner types into a form affects those numbers.

Anything that stops that one exchange completing inside the timeout is recorded as offline, which is why a server can be perfectly playable and still show grey.

Common causes

The server is genuinely down — restarting, updating, or the host has stopped it. Most restarts are short enough that the next cycle picks the server back up on its own.
A firewall is blocking us. Some hosts block datacentre ranges outright and some rate-limit status pings hard enough that ours is dropped. If players can join fine but we show offline, this is almost always the reason.
The address changed. A server that moved keeps answering on its new address while the listing still points at the old one. Edit the listing.
DNS problems. An expired domain, a broken SRV record or a nameserver change that has not propagated makes the address unresolvable even though the machine behind it is fine.
Wrong edition. A Bedrock server listed as Java gets a TCP connection and a Java handshake and will never answer. Fix the edition and it comes straight back.
Wrong port. Bedrock does not read SRV records, so a Bedrock listing without the correct port fails every single time.
The status response is disabled. Rare, but enable-status=false in server.properties switches off exactly the reply we depend on. If your server does not appear in the in-game server list either, that is your answer.
The proxy is up and the backend is not. On a network running Velocity or BungeeCord the proxy answers pings by itself, so this shows as online with zero players rather than offline.

Things that are not the cause

A whitelist does not block status pings, so a whitelisted server still reports online. Neither does a full server, a join queue, or premium-only mode. If your server is up and reachable and we say otherwise, the problem is between us and the port rather than inside the game.

Getting a listing back

Fix whatever the cause was and wait for the next ping cycle. The listing updates by itself and there is nothing to press. A server that fails every ping for a long stretch drops out of the active list rather than sitting there advertising a dead address, and editing the listing once the server is up again brings it back into rotation.

If you are certain the address is right and we still cannot reach it, ask your host whether status queries from outside are being filtered, then tell us so we can look at it from our side. Adding your server covers the same check at submission time, which is where most of these problems surface first.

If you are a player

Try connecting anyway. Our ping can fail for reasons that have nothing to do with whether you can join, and the address shown is still the right one. If it turns out to be genuinely dead, let us know and we will look at the listing. A server that is offline every time you check across a week is worth giving up on — there are plenty of others in the same gamemode.