spark Mod (1.21.11, 1.20.6) – Diagnose Your Game's Problems

Spark is a performance profiling mod that helps diagnose lag, high CPU usage, and memory problems on Minecraft clients, servers, and proxies, available for Fabric, Forge, NeoForge, and Quilt mod loaders.

Every Minecraft player and server owner eventually hits the same wall: something is lagging, and you have no idea why. Is it a specific mod? A chunk loading issue? A memory leak from a poorly optimized resource pack? Without a profiler, you are essentially guessing — restarting the server, removing mods one by one, and hoping something sticks. Spark solves this by giving you precise, actionable data about what your game or server is actually doing under the hood. With over 13.8 million downloads on Modrinth alone, it has become the de facto standard for Minecraft performance diagnostics. Developed by lucko, the same developer behind LuckPerms, Spark has earned a reputation for reliability and ease of use across the entire Minecraft modding community.

Key Features of Spark

• CPU Profiler — This is Spark's flagship feature. It samples your game or server's activity and builds a detailed call graph showing exactly which code paths are consuming the most processing time. Whether you are tracking down a mod that tanks your tick rate or identifying a plugin that causes periodic lag spikes, the CPU profiler gives you a clear visual breakdown in an online viewer. Running it for roughly 30 seconds is typically enough to surface the most problematic areas.
• Memory Inspection (Heap Summary) — Spark can take a snapshot of your JVM's heap memory, showing you which classes are using the most memory and how many instances exist. This is invaluable when your server's RAM usage keeps climbing and you need to figure out whether it is a mod leak, excessive entity counts, or cached data that never gets released. The summary view is designed to be quick and readable without needing external analysis tools.
• Heap Dump Export — For deeper analysis, Spark can export a full HPROF heap dump that you can open in dedicated memory profiling tools like VisualVM or Eclipse MAT. This goes beyond the built-in summary and lets you trace object references and allocation paths. Spark can optionally compress the dump file, which is helpful given that heap dumps from modded servers can be several gigabytes in size.
• Server Health Reporting — Spark continuously monitors your server's tick rate, CPU usage, and memory consumption, letting you keep an eye on overall health in real time. Rather than waiting until players complain about lag, you can proactively spot degradation trends before they become serious. This is especially useful for larger servers that run dozens of plugins or mods simultaneously.
• Lightweight and Production-Safe — According to the developer, Spark is designed to run in production environments with minimal overhead. It does not require complex configuration or setup — you install it like any other mod, and the profiling commands are available immediately. This means you can leave it installed as a permanent diagnostic tool rather than only adding it when problems arise.
• Dual Profiler Engines — Spark offers two different profiling backends: a native AsyncGetCallTrace engine powered by async-profiler for Linux systems, and a built-in Java ThreadMXBean engine that works on all platforms. The native engine provides more accurate results on supported systems, while the Java-based engine ensures broad compatibility across Windows, macOS, and Linux.
• Online Viewer with Deobfuscation — Profiling results are displayed in Spark's web-based viewer, which presents the call graph as an intuitive tree structure. The viewer can apply deobfuscation mappings, meaning you see readable method names instead of cryptic obfuscated identifiers. This makes analysis accessible even if you are not deeply familiar with Minecraft's internals.

Screenshots

How to Install Spark

1. Make sure you have a compatible mod loader installed. Spark supports Fabric, Forge, NeoForge, and Quilt — choose the one that matches your modpack or server setup.
2. Download the correct Spark version for your Minecraft version and mod loader from the official Spark website or Modrinth page.
3. Place the downloaded .jar file into your mods folder. For servers, this is in the server root directory; for clients, it is in your .minecraft/mods folder.
4. Launch Minecraft or start your server. Spark registers its commands automatically — no configuration files to edit.
5. Use /spark profiler to start a CPU profile, or /spark health to check server health. Results are uploaded to the Spark viewer where you can analyze them in your browser.

Requirements & Compatibility

What's New

• Updated to support Minecraft 26.1 across Fabric, Forge, and NeoForge loaders.
• Latest version published on Modrinth on March 26, 2026.
• Continued maintenance and compatibility updates since initial release in June 2021.
• Full changelog and version history available on the official Spark website.

Pros and Cons

Alternatives to Spark

• Observable — A server-side performance monitoring mod that shows per-entity and per-block-entity tick times, useful for identifying specific lag sources in your world rather than code-level profiling.
• Chunky — A chunk pre-generation mod that helps prevent lag caused by on-the-fly chunk generation, complementing Spark's diagnostic capabilities by eliminating one of the most common server lag sources.
• FerriteCore — A memory optimization mod that reduces Minecraft's RAM usage, which pairs well with Spark's memory inspection tools to both diagnose and resolve memory-related performance issues.

Download Spark

Always download mods from official sources to stay safe.

Frequently Asked Questions

Is Spark safe to use on a production server?

Yes — Spark is designed to be lightweight enough for production use. The developer states it can run with minimal impact on server performance, and many large public servers keep Spark installed permanently as a diagnostic tool. It only actively consumes resources when you run a profiling command.

Does Spark work on the client side or only on servers?

Both. Spark works as a client-side mod for diagnosing FPS issues and rendering bottlenecks, and as a server-side mod for profiling tick rate, plugin performance, and memory usage. You can install it in either or both environments depending on your needs.

Can I use Spark with Fabric and Forge mods at the same time?

No — you need to download the version of Spark that matches your specific mod loader. Fabric, Forge, NeoForge, and Quilt each have their own Spark builds. However, the profiling results and web viewer work identically regardless of which loader version you use.

Does Spark support Minecraft 26.1?

Yes — Spark was updated on March 26, 2026 with full support for Minecraft 26.1 across Fabric, Forge, and NeoForge. It also maintains backward compatibility with versions as old as 1.16.5, covering a wide range of modded setups.

How long do I need to run a Spark profile to get useful results?

Around 30 seconds is typically sufficient. According to the mod's documentation, a short sampling window is enough to identify the most significant performance bottlenecks. For intermittent lag spikes, you may want to run longer sessions or use Spark's option to record only during laggy periods for more targeted results.

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