Flare (Spark for 1.12.2)
by Cleanroom
Flare is a Forge 1.12.2 tool for finding lag, high CPU usage and memory problems, derived from Spark and run under the Cleanroom environment.
What it does
Flare samples a running server or client and builds a call graph from the collected statistics, so a player or administrator can see which code paths consume time. Its two profiler engines are a native mode using AsyncGetCallTrace with perf events, which relies on async-profiler and is only available on Linux x86 64 systems, and a built-in mode based on Java ThreadMXBean. The call graph can be viewed in an online viewer, where mapping deobfuscation is applied to the results.
The tool is meant for problems such as low tick rate, high CPU usage and general lag. Flare includes memory inspection tools for finding memory issues on a server, and a health report that summarises overall server state, including tick rate averages and individual tick monitoring. Flare is an improved version of the WarmRoast profiler by sk89q and is made up of separate components.
Flare is published for Forge only, for 1.12.2 only. Either side can run it, and neither needs it. It is open source under the GNU Lesser General Public License v3.0 only. Its latest Forge file is 0.8.0, a beta build dated 2026-04-02.
Key features
CPU profiler
Samples threads at a chosen interval and records only the laggy periods, so a short run can reveal where time is spent.
Memory inspection
Provides a set of tools for finding memory problems on a running server.
Server health reporting
Produces a report summarising overall server health, with tick rate averages and monitoring of individual ticks.
Readable call graph
Results form a simple tree structure that is straightforward to analyse, and the online viewer applies deobfuscation mappings.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Diagnosing lag
Running the profiler for about 30 seconds is often enough to produce useful insights into the areas causing performance problems.
Monitoring a server
Server owners can use the health report to keep track of overall server health while the server runs in production with minimal impact.
Who it’s for: Server owners and modpack developers on Forge 1.12.2 who need to find the causes of lag, high CPU usage or memory growth. Players who run a client can use it as well.
Questions
Which Forge version does Flare support?
Does the native profiler run on every operating system?
Does Flare have to be installed on the server?
In the catalog
Flare (Spark for 1.12.2) is one of 3,514 Library mods on ModsFinder, and one of 1,576 Library mods for Forge. 2,920 mods support Minecraft 1.12.2.
More from Cleanroom
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What the author says
Derived from spark; flare is a performance profiler and debugger for 1.12.2 Forge & Cleanroom environments. flare's profiler can be used to diagnose performance issues: "lag", low tick rate, high CPU usage, etc.
Official listing
- Modrinth page
- modrinth.com/mod/flare
- Owner
- Cleanroom
- Published
- 2024-08-19
- Updated on Modrinth
- 2026-04-02
- Facts verified
- 2026-10-15