Engine Build
WebKit 20620.1.15
JSC Tiered JIT (FTL Enabled)
Host Navigator
Safari / WebKit
macOS Sequoia (Darwin 24.x)
Graphics & Compute
Metal 3 (WebGPU / WebGL2)
OffscreenCanvas HW Accelerated
STP 251 Health Index
98.4 / 100
+4.2% vs Safari 18.2 Stable
Micro-Benchmark Lab
Idle / ReadyJavaScriptCore JIT & Memory Pressure
Prime sieving, TypedArray allocations, and structured clone hops
--
ops/sec
CSS Subgrid & Layout Recalculation
Nested grid track alignment, dynamic DOM mutations & container queries
--
ms avg
Canvas 2D & Render Pipeline Latency
10,000 active particle vectors, blend modes, and repaint jitter
--
FPS
STP 251 Feature & Regression Suite
0 / 8 TestedRelease Delta Matrix: STP 251 vs Safari Stable Baselines
Reference Profile: M3 Max / Sonoma 14.6
JavaScriptCore JIT Execution
+14.2%
ArrayBuffer Structured Serialization
1.22 ms-18%
RegExp Tier-2 FTL Match Throughput
84.2k ops/s+9.4%
Microtask Drain Queue Latency
0.04 ms0.0%
CSS Engine & Subgrid Recalculation
+22.8%
Deep Subgrid Inherited Track Alignment
3.8 ms-31%
Container Query Size Mutation Reflow
2.1 ms-14%
CSS text-box-trim Glyph Box Bounding
Native PassNew
Graphics & WebGPU Composition
+8.6%
Canvas 2D Path2D Cache Invalidation
60.0 FPS+5.2%
OffscreenCanvas Worker Transfer
0.18 ms-24%
WebGPU Pipeline Compilation Overhead
12.4 ms-11%