LagSense

LagSense

Find what's slowing down your Minecraft server, directly in-game.

LagSense is a performance profiler for Minecraft NeoForge, inspired by LagGoggles, spark and Observable. It combines detailed server profiling with world visualisation to help locate and investigate performance problems.

Features

Help players investigate their own bases

Players can inspect reports captured by server admins or automatic captures. Optional FTB Teams / FTB Chunks and Open Parties and Claims integrations restrict player results to their permitted claims. Admins can also define public profiling areas. Players cannot start server captures or change server settings.

Visualise lag directly in-game

View measured entities, blocks and chunks in the world, including through walls. Inspect timings, follow moving entities and explore hotspots using the chunk heatmap. Captured timings remain fixed until another profile is taken.

More than ticking entities

Investigate directly measured entity, block entity, scheduled tick, random tick and NeoForge event-handler timings. Explore sampled CPU activity and Java call paths on the server thread and background threads. Group results by mod, type or individual target.

Capture, save and compare

Run profiles manually, schedule them or trigger captures after sustained lag spikes. Optionally save profile history and compare captures to investigate improvements and slowdowns. Saved reports remain available after server restarts when history is enabled.

Discord reporting

Send performance summaries containing TPS, MSPT, severity, expensive contributors and chunks. Configure role mentions by severity and optionally attach one complete HTML, JSON or CSV report. Attachments default to None.

Reports can also be exported as standalone interactive HTML files that work offline, without an external website or account. In-game reports include search, grouping, historical comparisons, hotspot markers and operator-only teleport tools. Three UI themes and configurable HUD positioning are included.

Compatibility

Install LagSense on the server for profiling and on clients for report screens and overlays. Use the same LagSense version on both sides. Single-player requires one installation. Claim integrations are optional.

Getting Started

1. Install LagSense and start Minecraft or the server.
2. As an operator, run /lagsense profile to capture 30 seconds of server activity.
3. Open /lagsense report to investigate results. Other players receive only the results they are permitted to view.
4. Open Settings to configure captures, Discord delivery and profiling options. Server settings are restricted to operators.

Keyboard Shortcuts

Shortcuts can be remapped in Minecraft Controls. Hiding visuals preserves each individual display preference. Public-area creation helpers remain visible.

Commands

Capture, automation, configuration, Discord and teleport commands require operator access. Opening a report does not start a capture.

Public Areas

Operators can share captured results from an area with every player:

/lagsense area pos1
/lagsense area pos2
/lagsense area create area1

Stand at opposite corners when setting pos1 and pos2. Areas cover the selected X/Z footprint across the dimension's full build height. Use /lagsense area show or /lagsense area hide to inspect boundaries. /lagsense area delete removes the area you are standing in; overlapping areas require a name.

Public areas grant permission to view results, not to run captures or teleport. Claim ownership and membership are checked when results are requested. Where claim providers overlap, all claiming providers must permit access unless the area has been explicitly shared by an administrator.

Configuration and Measurements

Server settings are stored in config/lagsense-server.toml. Client display preferences are stored in config/lagsense-client.json. Operator settings can be edited in-game. Use /lagsense reload after editing server configuration on disk.

Scheduled captures, spike detection, history and Discord delivery are opt-in. Spike captures measure activity after detection, so they cannot recover a hitch that has already finished. Timers skip captures while another capture is running.

Direct timings cover supported calls across all ticking loaded chunks and loaded dimensions. Non-ticking chunks produce no measurements. CPU activity and call paths are execution samples, not exact timings. Event-handler timings are inclusive; the separate coverage calculation counts overlapping execution once. Background-thread samples do not contribute to server MSPT.

Capture and transfer budgets protect server and client memory. Reports identify incomplete captures, and oversized transfers or exports fail explicitly rather than silently removing results. HTML, JSON and CSV exports include all available retained data and can contain coordinates, entity UUIDs and server diagnostics.

License

LagSense is licensed under the MIT License.

Bundled Noto fonts retain their SIL Open Font License.

Font sources are listed in SOURCES.txt.