How to Increase IntelliJ IDEA Memory Allocation to Eliminate Lag

When using IntelliJ IDEA, many developers experience occasional lag even on machines with ample RAM because the IDE’s default maximum heap size is set very low (often 1 GB). This limited allocation causes performance bottlenecks when compiling or running large projects.

You can check the current memory consumption of your project via the IDE’s memory indicator, which in the example shows 690 MB used out of a 1024 MB limit.

Step‑by‑step solution

1. Open the custom VM options dialog: In the top menu select Edit Custom VM Options under Help . This opens the file where IDEA’s JVM parameters are defined.

2. Modify the memory settings: The default file contains lines such as:

-Xmx1024m    // maximum heap size (1 GB)
-Xms256m     // initial heap size
-XX:ReservedCodeCacheSize=128m
-XX:+UseG1GC

Adjust them according to your machine, for example:

-Xmx4096m
-Xms4096m
-XX:ReservedCodeCacheSize=256m
-XX:+UseG1GC

Save the file after editing.

3. Invalidate caches to apply the new settings: Choose File → Invalidate Caches , keep the default options, confirm, and restart IDEA.

After restarting, the IDE runs much more smoothly.

These same memory‑tuning steps work for other JetBrains tools such as PyCharm, Android Studio, and WebStorm.

Additional JVM parameters (e.g., -Xms , -Xmx , -XX:PermSize , -XX:+UseParNewGC ) are listed for reference, useful when the heap size is large and major garbage‑collection pauses become noticeable.