G1GC vs ZGC vs Shenandoah for Minecraft Servers

Why the GC Choice Matters

The garbage collector you choose determines how your server handles memory cleanup. A poor choice means long pauses and lag spikes. The right choice means near-invisible GC with smooth TPS. This g1gc vs zgc minecraft comparison covers the three collectors most relevant to Minecraft servers in 2026.

G1GC (Garbage-First Garbage Collector)

G1GC is the default collector for most Minecraft setups and the one recommended by Aikar's flags. It divides the heap into regions and collects the most garbage-filled regions first, hence "garbage first."

Strengths

• Well-tested with Minecraft workloads.
• Aikar's flags provide a proven tuning profile.
• Works well with heap sizes from 2 GB to 12 GB.
• Low CPU overhead compared to the other options.

Weaknesses

• Pause times increase with heap size. Above 12 GB, pauses can exceed 100 ms.
• Full GC events are rare but devastating when they occur.

Best For

Servers with 2 to 12 GB of heap and up to 50 players. This covers the majority of community servers.

ZGC (Z Garbage Collector)

ZGC is a low-latency collector designed for large heaps. Its pause times are typically under 1 ms regardless of heap size, making it ideal for servers where g1gc vs zgc minecraft becomes a relevant comparison, usually at 10+ GB.

Strengths

• Sub-millisecond pause times, even with 32+ GB heaps.
• No full GC events.
• Scales linearly with heap size.

Weaknesses

• Higher CPU usage (5 to 15% more than G1GC).
• Higher memory footprint. ZGC uses colored pointers that add overhead.
• Less community testing with Minecraft compared to G1GC.

How to Enable

java -Xms14G -Xmx14G -XX:+UseZGC -XX:+ZGenerational ...

On Java 21+, use -XX:+ZGenerational for the improved generational ZGC mode, which reduces CPU overhead significantly.

Best For

Servers with 12+ GB heap where GC pauses from G1GC are noticeable. Large networks, heavy modpacks, and 50+ player servers benefit most.

Shenandoah

Shenandoah is an alternative low-pause collector developed by Red Hat. It shares ZGC's goal of sub-millisecond pauses but uses a different approach (Brooks pointers instead of colored pointers).

Strengths

• Sub-millisecond pauses similar to ZGC.
• Available in OpenJDK builds from Red Hat and Adoptium.
• Slightly lower memory overhead than ZGC in some workloads.

Weaknesses

• Not included in Oracle JDK. You must use an OpenJDK distribution that ships it.
• Higher CPU usage than G1GC.
• Least tested of the three with Minecraft workloads.

How to Enable

java -Xms14G -Xmx14G -XX:+UseShenandoahGC ...

Best For

Servers already using Red Hat or Adoptium OpenJDK builds where ZGC is not available or performs poorly. A viable alternative to ZGC with similar characteristics.

Comparison Table

Feature	G1GC	ZGC	Shenandoah
Typical Pause	10-50 ms	<1 ms	<1 ms
CPU Overhead	Low	Medium	Medium
Memory Overhead	Low	Medium-High	Medium
Ideal Heap Size	2-12 GB	8+ GB	8+ GB
Maturity (MC)	Excellent	Good	Fair
JDK Availability	All	All	OpenJDK only

Our Recommendation

For most servers, start with G1GC using Aikar's flags. If you allocate 12+ GB and notice GC pauses in Spark reports, switch to ZGC with generational mode. Shenandoah is a solid fallback if ZGC is unavailable on your JDK distribution.

The g1gc vs zgc minecraft decision ultimately comes down to heap size. Below 10 GB, G1GC wins on simplicity and lower CPU usage. Above 10 GB, ZGC wins on pause time consistency. Monitor with Spark, check GC lag diagnostics, and let the data guide your choice.

See an optimized server in action: Astroworld MC, IP play.astroworldmc.com, Java + Bedrock.