Java Edition:
- Start your server as usual
- Switch to the console page: https://aternos.org/console/
- Type /seed into the console command field and press enter
Afterwards you can see the seed of your server in the console.
If nothing happens when you enter the /seed command into the console, make sure that your server is online as noted in step 1.
Bedrock Edition:
- Start your server as usual
- Join your server as usual
- Pause the game on your device
- Click the settings button on your device's menu
- Make sure "Game" is selected in right menu bar and scroll down until you see the seed
