Aternos server not starting or crashing: what to do

If your Aternos server won’t start, open the log first: it almost always tells you why. According to Aternos itself, the cause is usually the software on your server, such as a mod or plugin that doesn’t fit, rather than Aternos.

Below you’ll find how to read the log, the most common causes and what to do when your server is running but you can’t get in. Stuck in the queue or on Pending? That’s covered in Aternos queue, sleep mode and lag.

Step 1: read the log

When a start fails, you’ll see your server’s status jump from Starting to Stopping. The log lives on the Log page of the panel. Every line starts with a time and a level, such as INFO, WARN or ERROR. Look for the first ERROR line around the moment your server stopped. The lines around it often explain more, and quite often they name the mod or plugin involved.

At the top of the log page, Aternos shows automatic suggestions, sometimes with a button that fixes the problem on the spot. Try those first. Still stuck? Click Share in the top right. You’ll get a link to mclo.gs, a site Aternos built for sharing logs, which you can include when you ask for help from Aternos support or on a forum.

The most common causes

• A mod or plugin for another version. A mod for 1.21.1 won’t start on 26.3, and a Fabric mod won’t run on NeoForge. Pick the version that matches your server, or remove it.
• A missing dependency. Lots of Fabric mods need Fabric API. The log usually names the mod that’s missing.
• A client-only mod. Mods for visuals and performance belong on your own PC, not on a server, and they can stop it from starting.
• Just added something? Remove the last thing you installed and start again. If it works now, you’ve found the culprit.
• A log that fills up. If your log grows too large, Aternos stops your server. According to Aternos, broken plugins or mods, or command blocks, are usually to blame. For command blocks, /gamerule command_block_output false helps (before Java 1.21.11: commandBlockOutput).
• A full server. Your server can be up to 4 GB on Aternos. Hit that limit and you get an error message when you start it. Turn on the Optimize option for your world, which deletes unused chunks, and remove worlds, mods or plugins you no longer use.

On Aternos you install mods and plugins from its own library, which draws on CurseForge and Modrinth among others. A mod’s page tells you which loader and version it’s for. Here’s how to read that: CurseForge vs Modrinth.

Step 2: restore a backup

If things broke after a change, a backup is the quickest way back. Aternos keeps backups in your own Google Drive:

1. Link Google Drive in your account settings or on your server’s Backups page.
2. Add that storage to your server with the + button on the Backups page.
3. Turn on automatic backups. Aternos then makes one whenever your server stops, up to a limit you set.
4. Click Restore on the backup you want back. This replaces all your server files, including your world.

It’s running, but you can’t get in

• Is it really online? The status should be green and say Online. Refresh the page to be sure.
• Try again. According to Aternos, a second attempt after a long error message often just works.
• Use the DynIP. Under Connect (the i icon on Bedrock) you’ll find a direct address. It changes every start, but it sidesteps DNS problems.
• Bedrock? Use port 19132. Aternos is moving Bedrock servers to the new NetherNet network protocol. Anyone with an old port saved in their server list won’t be able to get in.
• Mods on the server? Then you need exactly the same mods, in the same versions. For a modpack, play the same pack version through the launcher it belongs to.
• Incompatible client. If you see “Incompatible client! Please use...”, you’re on a different version from your server. Pick the same version in your launcher, or switch the server to yours.
• Failed to verify username. Close Minecraft and every launcher, start again, and restart your PC if needed. Changed your name recently? Log out of the launcher and back in.

An ad blocker warning

Aternos is free because it runs entirely on advertising, so it detects ad blockers and asks you to switch them off. You can see that warning even without an ad blocker: privacy add-ons such as Ghostery or Privacy Badger, strict tracking protection in your browser, antivirus software or a filter on your router can all block the ads. Switch them off for Aternos.

Is Aternos itself down?

That happens too. On status.aternos.gmbh you can see whether the website, the game servers or the storage have a problem. If your server shows Pending, the machine underneath it is briefly unreachable. Aternos is notified automatically, so waiting is your best bet.

Has your server disappeared?

Aternos deletes servers that haven’t been started for a while, usually after about three months. If your account has an email address, you’ll get a warning a few days beforehand, and pressing Start once is enough to keep it. Already gone? Check Previous servers on your servers page. You can only restore it from a backup: without one, even Aternos support can’t bring it back.

When does your own server make more sense?

Aternos is a decent, free place to start, and you can fix most start problems yourself using the log. If you keep hitting the same limits, such as the queue, a server that shuts down when everyone leaves or a mod that isn’t in the library, your own server starts to look attractive. What you gain and what it costs is covered in Aternos alternative: when is a paid server worth it? Your world comes with you: download it under Worlds and follow How to move your Minecraft world to your own server.