Light Core
by Stormglyph
Light Core is a client-side performance monitor for Fabric that samples frame rate, memory and CPU use and reports a single score from 0 to 100 with a short message.
What it does
The monitor averages the client frame rate over a short rolling window, then records JVM heap use against its maximum, physical memory use against the total, CPU load percent and the CPU core count. Operating system, architecture and Java version are logged as context, so a result can be read against the machine it came from.
Those samples feed a weighted evaluation that starts from the frame rate and subtracts penalties for memory pressure, CPU load and core count. The outcome is a score from 0 to 100, placed in one of four tiers: Excellent, Good, Average or Low. A short message accompanies it, for example pointing to low frame rate, high CPU load or high memory pressure. Results can be logged and ranked, which suits comparing settings across runs.
Light Core requires Fabric API and runs on Fabric for Minecraft 1.21.4 – 1.21.11, with files for eight release versions. Only the client needs it, so servers run without it. The code is not open source, and it is released under All rights reserved.
Key features
Frame rate sampling
The client frame rate is averaged over a short rolling window, smoothing out single spikes in the readings.
Memory and CPU readings
JVM heap use, physical memory and CPU load are sampled alongside the core count to show where the pressure comes from.
Weighted score
A score from 0 to 100 combines the frame rate with penalties for memory pressure, CPU load and core count, mapped to four tiers.
Actionable messages
Each result carries a short note suggesting a likely cause, such as low frame rate or high memory pressure.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Requirements
Dependencies declared by the latest file for each loader.
Required 1
Use cases
Who it’s for: Players who want to measure their own client's performance, and modpack authors who check how a pack runs on different hardware. The mod is only needed on the client.
How it compares
Improved F3 is client-side only, released under CC0 1.0 Universal, and published for 1.21.6 – 26.3, extending the debug screen rather than producing a score. Prism Performance is client-side only under the MIT License for 1.21 – 1.21.11, and is not open source. Gpu Cpu Util is open source under the MIT License for 1.21 – 1.21.11, and is client-side only.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Light Core | Fabric | 1.21.4 – 1.21.11 | Client-side only | 2026-03-20 |
| Improved F3 | Fabric | 1.21.6 – 26.3 | Client-side only | 2026-10-11 |
| Prism Performance | Fabric | 1.21 – 1.21.11 | Client-side only | 2026-03-23 |
| Gpu Cpu Util | Fabric | 1.21 – 1.21.11 | Client-side only | 2026-01-09 |
Questions
Does Light Core need Fabric API?
Does the server need Light Core?
Which versions have files for Light Core?
In the catalog
Light Core is one of 3,545 Optimization mods on ModsFinder, and one of 2,575 Optimization mods for Fabric. 19,862 mods support Minecraft 1.21.11.
Similar mods
Official listing
- Modrinth page
- modrinth.com/mod/light-core
- Owner
- Stormglyph
- Published
- 2026-03-20
- Updated on Modrinth
- 2026-03-20
- Facts verified
- 2026-10-15