When your computer's memory is running low, Minecraft may not be able to allocate the amount of memory that you specify. The most common reason for this is that other applications are using up a lot of your computer's memory.
Step 1: Close other applications
- Open Task Manager. This can be done quickly by pressing the Ctrl, Shift, and Esc keys at the same time.
- In the "Processes" menu, look for applications that you are not using. Click on them, then press "End task".
Make sure you do not close any important system processes. If you are unsure about something, it is best to leave it alone.
Step 2: Lower allocated memory
- Open the Lunar Client launcher.
- Press the "Settings" button at the top.
- Move the slider under the "Allocated Memory" section to the left.
The standard 3.0GB is usually enough, but you may need to lower this value slightly depending on the amount of total RAM available on your computer. You should not go below 1.0GB or above 4.0GB.