Vitals

Vitals

A clean, minimal performance overlay for Fabric — built to tell you not just how fast
the game runs, but what caused that stutter.

What it shows

• FPS — read from the game’s own counter, so it always matches vanilla and other tools
• 1% low FPS and frametime p50 / p99 percentiles (the numbers that actually feel like smoothness)
• Frametime sparkline with adaptive scale — spike bars are colored by their cause
• Server tick budget — how much of the 50 ms tick the integrated server uses (singleplayer)
• Heap usage and GC activity — last pause duration and time since
• Spike attribution — when a frame spike happens, Vitals tells you who did it:
• gc (amber) — garbage collector pause overlapped the frame
• tick (blue) — the integrated server tick ran long
• render (red) — everything else (graphics-bound)

Benchmarking

Press F9 to export the whole session (up to 2048 frame samples + summary statistics)
to .minecraft/vitals/*.csv. Header lines start with #, so pandas
(comment='#') and spreadsheets read it cleanly. Perfect for A/B testing JVM flags,
mod configs, or graphics settings — compare p99 and 1% lows, not averages.

F8 toggles the overlay. Keys are rebindable in Controls.

Design principles

• Numbers wear neutral ink; color only appears where it carries meaning (status dot, budget bar, spike bars). No rainbow HUD.
• Zero mixins — pure Fabric API. Nothing to conflict with your other 100 mods.
• Near-zero overhead: no per-frame allocations, text refreshes at 2.5 Hz, primitive ring buffers throughout. A performance tool must not cost performance.

Methodology notes (honest fine print)

Since Minecraft 26.x, HUD rendering is decoupled from the frame loop, so Vitals
samples the game’s own per-frame timer instead of timing its callback. Percentiles
are statistically valid estimates; any stall longer than the sampling interval is
always captured. Spike attribution is a well-informed heuristic, not a profiler proof.
For deep profiling, use spark — Vitals is the always-on dashboard, not the microscope.

Requires Fabric API and Java 25 (Minecraft 26.2+).