Quick answer: Frame rate is how many frames per second your game renders; frame time is how long each individual frame takes, in milliseconds. They're inverses, but frame time reveals individual slow frames that an averaged FPS hides.
Frame rate and frame time are two ways to express the same underlying thing, rendering speed, but they're useful for different purposes. For diagnosing performance, the distinction matters. Here's the comparison.
What Frame Rate Measures
Frame rate, frames per second (FPS), is how many frames your game renders each second, the familiar 30, 60, or 120 FPS. It's intuitive and good for communicating a target ('runs at 60 FPS'). But frame rate is usually reported as an average, which smooths over individual slow frames, hiding the hitches players actually feel.
Bugnet captures performance data so you can see frame rate, but an averaged FPS can be misleading: a game averaging 60 FPS can still stutter badly if some frames are slow. Frame rate is good for headline targets, less good for diagnosing the inconsistency that causes stutter.
What Frame Time Measures
Frame time is how long each individual frame takes to render, in milliseconds, 60 FPS corresponds to about 16ms per frame. Frame time is the per-frame view, and it's more useful for diagnosis because it reveals individual slow frames: a single 40ms frame is a visible hitch, even if the average frame rate looks fine.
Bugnet's performance snapshots capture frame-time data, so you can see the spikes, the individual frames that overran, not just the average. Frame time is the diagnostic-level measurement: it exposes the variance and worst frames that frame rate, especially averaged, conceals.
Why Frame Time Is Better for Diagnosis
They're mathematically inverses (frame time = 1000 / FPS), but frame time is better for finding performance problems because it shows individual frames. Stutter and frame drops are about specific slow frames, which frame time reveals and averaged frame rate hides. To diagnose performance, look at frame times and the worst frames, not just average FPS.
Bugnet captures frame-time spikes and what the game was doing when they happened, so you target the slow frames causing stutter. So use frame rate for communicating targets, but frame time for diagnosis, since the per-frame view exposes the spikes and inconsistency that an averaged frame rate would smooth over.
Frame rate is frames per second (good for targets); frame time is milliseconds per frame (good for diagnosis). They're inverses, but frame time reveals individual slow frames that an averaged FPS hides.